The following extracts are taken from the Annual Reports of the Astronomer Royal to the Board of Visitors.
The reports were presented at the annual visitation, which normally took place in the first week of June. The first was produced in 1836. The report for the following year established a format that remained much the same until 1963, (the year before the Board was abolished).
The reports from 1837 onwards were grouped into nubered sections dealing with different topics. Both the number of sections and their names evolved over time. Relevant extracts from the varoius sections are reproduced here. There may be inadvertent omissions.
Although the twelve clocks by Dent purchased for the 1874 Transit of Venus expeditions were considered to be amongst the principle portable instruments owned by the Observatory, the listing of their locations in the section 'Buildings and Grounds, Moveable Property, and Library' is remarkably inconsistent. Those at Greenwich were often omitted as were some of those that were out on loan.
Whilst every effort has been made to check for transcription for errors, the text is not guaranteed error free. Most of the reports as published can be accessed on-line via this link.
The Report on the Royal Observatory … is intended to give an account of the state of the Observatory on 1869, May 10, and of the general history of the Observatory from 1868, May 6, to 1869, May 10.
I. Buildings and Grounds:-
The Chronometers were removed from the room above the Principal Computing Room to the middle story of the South-East [Great Equatorial] Dome, at the end of July 1868; and the room was fitted with desks, &c., and is now used as Second Computing Room for the Supernumerary Computers.
The channels for conveyance of the galvanic wires across the Front Court (connecting the Computing Room, the Altazimuth, the Transit-Circle, the Transit-Clock, the new Chronometer-Room, the S.E. Equatoreal, and its Chronometer, with the Chronograph, the Normal Mean Solar Clock, the Time-Signal-Ball, External Clocks, and External Time-Signals) have been considerably enlarged.
The Middle Room of the South-East Dome is now completely fitted up as Chronometer-Room, with ample accommodation of Tables for Chronometers, with large Chronometer-Oven, and with exposed railed outhouse for chronometers to be placed in the open air. The scale of all these permits us to place the chronometer-boxes, if we think fit, with their lids open, and with the box-fronts towards the observer. The adjustment of the heat of the oven is easy and accurate.
V. Astronomical Instruments: -
The clocks generally are in good order.
Two ounces of quicksilver were added to the bulb of the Transit-Clock-pendulum, and it does not appear to require more. Lime is used, as I mentioned in the last Report, to keep the air in the head of the clock dry; it is changed once each month.
The East Dome Clock (Earnshaw) has been cleaned, and an alteration has been made in its spring-suspension, to remedy a wabbling motion of the pendulum.
The Ball Clock (Graham 3) has been cleaned.
A new clock by Messrs. Dent is in progress. It is to be constructed with an escapement analogous to the chronometer-escapement, which produces maintaining power with a smaller amount of friction than any other. I have arranged a method of altering the rate without stopping or touching the pendulum, by a sliding weight upon the crutch-rod, I am endeavouring also to prepare a construction for altering the thermal compensation through a small extent, without touching the pendulum. I have not succeeded to my satisfaction in planning a barometrical compensation. I propose to place the clock in the Magnetic Basement, where the temperature is more uniform than in any other of our rooms, and to lead galvanic wires from it to the Transit-Clock and other clocks.
The Motor Clock (Shepherd's) for Mean Solar Time, by which time-signals are given and received, and sympathetic clocks are maintained in action, is in good order. The sympathetic clock used for chronometer-rating has been transferred to the new chronometer-room; and two new sympathetic dials have been mounted there, showing seconds only. A clock by Dent, used for chronometer-comparisons only when the galvanic process fails, has also been removed to the new chronometer-room,
The Chronograph Barrel-Clock and the Chronograph generally are in good order.
XIII. Chronometers, Communications of Time, &c.:-
The number of chronometers on hand is 188, namely, III box chronometers, 23 pocket chronometers, and 8 deck watches, the property of the Admiralty; and 46 chronometers, the property of chronometer makers, on the annual competitive trial.
We have tried and have delivered to the Admiralty a chronometer to be used in trial of the speed of ships, and we have tried and reported on two chronometers intended for use in heaving the log.
All matters of expense on Government chronometers, whether for purchase or for repair, are referred to me in the first instance. The system of valuation and examination is founded upon the practice of rating all the chronometers, the greater part daily and others 'weekly, both in the open chronometer-room, whose daily range of temperature rarely exceeds 2°, and in the oven, where a temperature not exceeding 90° is steadily maintained.
The issues of chronometers to the Royal Navy are effected, for the most part, by sending them with balances wedged, in hampers under the Observatory seal, by ordinary railway conveyance, to the Admiralty agents at the outports. Scarcely an accident has occurred in this transmission. I am desirous, however, of seeing some apparatus arranged, by which the chronometer balance can be securely grasped, without the necessity for inserting cork wedges.
The experience of the use of bright white steel springs instead of blue springs, as preservative against rust, is favourable, but not decisive.
The error-number for chronometers under trial in the year 1868 is larger by an accidental quantity than that in the last two years; it is much smaller than it was five or six years ago.
The Motor Clock, and the entire system of communication of time from it by galvanic signals almost to the extremities of Britain, are in perfect order. For the difficult communication to the Time Signal Ball at Deal, for which alone I am responsible, the report of success is as follows: on 92.4 per cent. the ball was dropped freely by the galvanic current; on 3.8 per cent., in damp weather, the current required the assistance of the attendant's hand; on 1.4 per cent. the wind was too high to permit the raising of the ball; on 1·6 per cent. the communications were interrupted; and on 0.8 per cent. (3 days) the ball was falsely dropped by telegraph-signals of the railway.
For the Great Clock at Westminster Palace, to which we send signals for the guidance of the attendant, and which reports its own time to us, the report is less favourable than last year; the number of errors under 1s is 56 per cent. of the whole; the number under 3s is 93 per cent. of the whole.
At the Lombard Street Post Office, the clock upon which the others depend, and which has a gaining rate, stops itself at Oh. Om, Os clock-time a few seconds before Greenwich Noon, and is released by our current at Greenwich Noon.
A clock at the India Store Department is now regulated by a current sent at every second from the Royal Observatory.
There has been no farther correspondence in reference to signals on the Start Point.
No determination of longitude has been made by galvanic signals in the past year.
XV. Extraneous Work:-
The approach of the Transits of Venus has made it a duty of official astronomers to consider what steps ought to be taken now in preparing for their observation. I have with much care and with the consumption of much time examined into the circumstances of the two transits, and have come to the conclusion, that after every reliance is placed on foreign and colonial observatories, it will be necessary for the British Government to undertake the equipment of five or six temporary stations. It is much to be desired that authority should. be promptly given for procuring the instruments which will be required. On those by which local time and longitude will be determined, there is no uncertainty; on the viewing telescopes there may be some question. Still I conceive that it may be assumed as beyond doubt that a 6-inch telescope and a second telescope ought to be provided for every station.
Questions relating to the two East Indian Observatories have sometimes been placed before me by the Government. The clock required for the transmission of galvanic time-signals from the Observatory of Colaba (Bombay) has been sent to India, and clocks for a similar purpose at Madras are in course of construction.
XIV.– Personal Establishment:–
Mr. Ellis has the sole charge of the Time Department, Chronometers, Time Signals, and (quarterly) of Money Accounts; …
The view of the state of the Royal Observatory presented in this Report applies to its general condition on 1870, April 30. The interval of time included in its record of work done is the space of twelve lunations, beginning on 1869, May 11, and ending on 1870, April 30.
1. Buildings and Grounds:-
No alteration has been made in the upper rooms of the Magnetic Observatory. But the staircase which leads down into the Magnetic Basement, and which was inclosed in the upper story by pannelled sides and a door, has now also been inclosed in the lower story by pannelled sides and a door. We have strong reason for believing that this arrangement contributes sensibly to cut off the communication with the changing atmosphere of the upper regions, and thus to maintain uniformity of temperature in the Basement.
Signs of dry rot were lately remarked in the floor of the Basement. As the floor supports nothing important, the injury is limited to a possible giving way of some planks; none, however, has yet occurred. To promote ventilation for the future, I have removed portions of some of the planks so as to leave long narrow chinks across the room, which give very free passage of ail', without inconvenience to the feet.
V. Astronomical Instruments:-
The Transit-Clock is in good order. Its compensation for temperature is now satisfactory.
An alteration has been made in the mounting of the contact-springs (by which the clock completes a galvanic circuit at every second) so as to permit their removal and restoration without disturbing the dial or the seconds' hand.
The surfaces of each pair of the contact-springs, which formerly were both of platinum, are now one of platinum and one of gold. In the western pair, the platinum is connected with the zinc pole of the battery; in the eastern pair, the platinum is connected with the graphite pole. We hope by one of these arrangements to preserve the platinum from the injury which it receives from the galvanic spark.
A stiffer spring has been applied to the pendulum-suspension.
We are still occasionally troubled with rust on the steel portions of the transit-clock.
This had been partly prevented by the introduction of lime; but another inconvenience has thus been introduced, that of the dissemination of lime-powder over many parts of the clock-mechanism. For the present, the application of lime is discontinued.
The other clocks are in good order. The new clock to be constructed by Messrs. Dent, of 61, Strand, is not yet finished.
The Motor Clock for Mean Solar Time, with its six sympathetic clocks, and all the apparatus for giving and receiving galvanic signals, are in good order. The galvanic communication with the clock in the Royal Hospital Schools has become bad; and it is probable that the wires may be entirely removed.
The Chronograph-Barrel has required some repair from Messrs. Dent. The pivot-holes of the pricker-levers had become much enlarged; and the spindle of the rotating-lever which acts on the pendulum had been cut by the edges of the steel anti-frictionwheels. It is now in excellent order.
XIII. Chronometer’s, Communications of Time, &c.:-
Our chronometer-room contains at present 219 chronometers; namely, 150 box-chronometers, 23 pocket-chronometers, and 9 deck-watches, all belonging to the Government; and 37 chronometers which have been placed here by chronometer-rmakers as competing for the honorary reputation and the pecuniary advantages to be derived from success in the half-year's trial to which they are subjected. I take this opportunity of stating that I have uniformly advocated the policy of offering good prices for the chronometers of great excellence, and that I have given much attention to the decision on their merits; and I am convinced that this system has greatly contributed to the remarkably steady improvement in the performance of chronometers.
In the trial which terminated in August 1869, the best chronometers (taking as usual the average of the first six) were superior in merit to those of any preceding year.
All chronometers are rated daily till they are approved, and, afterwards, weekly; and all are tried some weeks in a temperature approaching to 90° Fahrenheit.
The labours of the Observatory are not confined to the rating chronometers and estimating their value; they include also the entire management of their repairs, the receipt of chronometers from all parties, and the issues to out-ports and to ships. A very great amount of labour is expended on these transactions, and on the necessary communications with the Admiralty and with chronometer-makers.
In sending chronometers, with their balances wedged, to all parts of the world, only one accident has been suspected. But several have arisen from the rude wedging by naval officers who send chronometers here. I hope to secure the assistance of an eminent chronometer-maker, which may lead to general adoption of a simple plan of his invention in the construction of the chronometer, intended to- dispense with this wedging, and which has been perfectly successful in two instances placed before me.
The experience of bright steel springs is still favourable to their preservation from rust.
Selections of chronometers have sometimes been made when required for purchase by the India Office and by other departments of Government.
The Greenwich Observatory Time Ball has been dropped with unerring regularity and accuracy. The public dial near the entrance gate of the Observatory, which is sympathetic with the "Motor Clock," and is worthy of all confidence, is now frequently used by the public for the comparison of chronometers.
The general system of communication of time-signals originating from our Motor Clock to nearly every part of the kingdom is in perfect order. In the communications to the Time Signal Ball at Deal, by a remarkably difficult telegraphic line, I find that, on 82.5 per cent. of days, the ball was dropped freely; on 10.7 per cent., with damp weather and a defective wire, the assistance of the attendant's hand (without appreciable error of time) was required; on 1.1 per cent., the violence of the wind made it imprudent to raise the ball; on 5.4 per cent., the communications were interrupted; and on a single day, the ball was erroneously dropped by telegraph-currents on the railway. On occasions like the last, a black flag is hoisted on the tower, to warn spectators of the ball-drop that an error has been committed. After these and all other failures, the hall is dropped by hand at 2h (the usual time being 1h).
In the Great Clock of Westminster Palace, the attendant on which receives timesignals from us, 44 per cent. of the errors are under 1s and 96 per cent. under 3s.
Time is efficiently given to the Lombard Street Post Office (where a clock which gave much trouble was found, on being transported to Greenwich, merely to have a lever slightly out of balance), and to the India Store Office.
In November 1869 I again took the sense of the Admiralty on the proposal to establish hourly time-signals on the Start Point. Their Lordships decided to maintain the former decision adverse to the proposal.
The telegraphs have not been used in the past year for the determination of longitudes. For this and similar purposes I remark that, as I understand, in the new subordination of telegraphs to the Post Office, the Post Office accepts all the customary engagements of the former proprietors of the telegraphs; and I have no doubt that, in case of need, every assistance will be given by that Department.
XV. Extraneous Work: -
The necessity of acting soon with reference to the Transit of Venus, 1874, was laid before the Government, who answered liberally to the appeal. With the funds placed at my disposal I purchased three 6-inch equatoreals, and have ordered two: I have also ordered altazimuths (with accurate vertical circles only), and clocks, sufficient, as I expect, to equip five stations.
Questions relating to the Colonial Observations are sometimes addressed to myself.
Occasionally also, trials of various proposals of clock construction and decisions on clock-expences, and, more regularly, trials of Navy Telescopes, are referred to the Observatory.
XIV.– Personal Establishment:–
He [the Astronomer Royal] is aided by … Mr. Ellis, with the Time Department and Money Accounts; …
The Report, now presented to the Board of Visitors, refers to the state of the Royal Observatory on 1871, May 4; giving an account of its general transactions during the interval of twelve and a half Iunations, included between 1870, April 30, the date of the last Report, and 1871, May 4.
I. Buildings and Grounds: -
In the Magnetic Observatory, the inclosure of the staircase which leads down into the Basement, by pannelled sides and a door in the lower story, has contributed materially in the last year to confine the changes of temperature in the Magnetic Basement within very small limits, by cutting off all currents of air from the external regions.
V. Astronomical Instruments:-
The Transit-Clock has lately been going very well. The remarkably severe weather of the past winter caused some sudden variations of rate, necessitating in one or two instances the separation, into two groups, of the morning and evening observations of the same day.
One pair of contact-springs has been withdrawn, the other by a re-arrangement of the batteries and wires being made to work both the Chronograph Pricker and the Sidereal clocks. This arrangement has been in action from March 10.
The clocks Graham 1 and 2, placed in the South Dome and Occasional Observatory respectively, were cleaned in August 1870, and some small repairs have at times been made to the galvanic clocks. The new clock by Messrs. E. Dent and Co. has not yet been received.
The Chronograph is in excellent condition.
XIII. Chronometers, Communications of Time, &c.: -
There are at the present time 202 chronometers in our chronometer-room, of which 123 box-chronometers, 21 pocket-chronometers, and 13 deck-watches, are the property of the Government; one, belonging to an officer of the Navy, is on trial for purchase; and 44 are placed here by chronometer-makers to take part in the annual tria1. The chronometers are compared with a Mean Solar Clock, some every day, some every week, sometimes in high temperatures, and sometimes in different magnetic positions, as usual.
Though the average of the trial numbers for the first six chronometers in the last competition shows a slight falling off in their merits, as compared with the previous year, one of the number was of unusual excellence.
The performance of chronometers, as depending on their mechanical construction, is very admirable; I have remarked but one point on which I could desire change, namely, that the balance should be struck more lightly, at a greater distance from its axis; the late Mr. Charles Frodsham, at my suggestion, had made some experiments on this point, which promised to be successful. The principal errors of even moderately good chronometers are, however, produced by defective compensation, which the most skilful makers cannot perfectly manage. I have long been of opinion that the final adjustment for compensation ought to be made by some more delicate operation than that which suffices for approximate compensation; but the able chronometer-makers whom I have consulted have not yet devised a satisfactory plan. Allusion was made in the last Report to a plan for securing the balance of a chronometer from injury in its transit by rail or otherwise. Nothing quite satisfactory has yet been proposed by any of the chronometer-makers who have turned their attention to the subject.
Chronometers have been selected, as usual, for purchase by the Admiralty, and occasionally for foreign men of science.
On eight days the Observatory Time-Ball was not raised on account of high wind; and once the drop failed from the piston not being properly discharged. On all other occasions everything has worked with the greatest regularity.
The public clock near the entrance gate of the Observatory has been cleaned and put in thorough order. All the wires concerned in driving the system of sympathetic clocks have been renewed.
Some repairs have lately been made in the mast of the Time-Ball at Deal. An improvement is to be remarked in the regularity of our communication with that Ball. On 89.4 per cent. of days in the past year the ball was dropped freely; on 4. 9 per cent., principally in damp weather, the current was too weak to release the trigger without assistance from the attendant; on 1.9 per cent. the wind was too high to permit the raising of the ball; on 3.2 per cent. communication was interrupted; on a single day the ball was falsely dropped by telegraph currents; while on another occasion a defect in the trigger (which has since been remedied) prevented the dropping of the ball.
A proposal has been made to have a ball dropped on the same plan at Queenstown, which can be done without any difficulty.
The report of the Westminster Clock shows that 55 per cent. of its errors are under 1s, and 94 per cent. under 3s.
The charge of the Lombard Street Post-Office Clocks has been transferred to the Telegraph Department of the Post-Office, time being communicated by the Observatory, and return signals being received here, as before.
In December two attempts were made to determine the longitude of Gibraltar, at the request of Professor Newcomb, but without success, the cable connecting Falmouth and Gibraltar being out of order. Every facility for these operations was given by Mr. Culley, Principal Engineer of the Post Office Telegraphs, and by Sir James Anderson, Managing Director of the Falmouth, Gibraltar, and Malta Telegraph Company.
XIV.- Personal Establishment:-
... Mr. Ellis takes charge of the Time Department (chronometers and galvanic communications) and Money Accounts; …
XV. Extraneous Work: -
My own time has been partly occupied in preparations for the Transit of Venus, 1874. I have taken measures for equipping each of five stations with a Transit, an Altazimuth, and an Equatoreal. Of transits I have five new, all mounted on stone piers. Of clocks to accompany them, I have two from the R. Observatory, three new. Of Altazimuths I have one from the R. Observatory, four new. Of Equatoreals, 6 inches in aperture, and carried by clock-work, I have five, purchased or new. Of clocks of an inferior class, to accompany the two last classes of instruments, I can supply only one, and must procure nine. Fifteen portable observatories must be prepared, of which I shall be able to exhibit specimens to the Visitors. The R. Observatory can supply three 4-inch detached telescopes, and two more will be desirable.
On the present occasion I offer the general history of the Observatory from the Full Moon of 1871, May 4, to the New Moon of 1872, May 7, including a period of twelve and a half lunations, and I report the state of the Observatory on the last-mentioned day.
I. Buildings and Grounds: -
The galvanic wires from the Battery Basement under the North Dome to the large clock at the Entrance Gate, which formerly were led round by the iron rails of the Front Court, are now led with many others under the pavement and under the floors of the Observatory Rooms, and are thence carried underground to the clock
In the Magnetic Observatory, ... I am making preparations for fixing a platform on the roof of the Magnetic Observatory for the observation of meteors, auroras, &c. The Normal Sidereal Clock, for giving sidereal time by galvanic communication to the Astronomical Observatory, was established in the Magnetic Basement in 1871, June; that locality being adapted for it on account of the uniformity of temperature. Further mention of this clock will occur in a following Section.
On 1871, December 1, the Watchman's Clock, upon which are registered the visits of the Night. Watchman, was moved from the Astronomical Observatory to the Magnetic Offices. As the Watchman, while not on beat, occupies the Gate Porter's Cabin, this arrangement insures the visits of the Watchman to every part of our now widely-extended premises. The clock-registers are read and entered in a book every morning.
II. Moveable Property: -
The six chronometers which were lent to the British Association Committee are all returned. [These were seemingly lent on 27 October 1871 (RGO6/784).]
V. Astronomical Instruments: -
The mechanical arrangements, as regards transits and time arrangements, have been completely modified by the introduction of the Normal Sidereal Clock. This clock is planted in the Magnetic Basement, as the locality in which the temperature is most uniform. Its escapement is one which I suggested many years ago in the Cambridge Transactions; a detached escapement, very closely analogous to the ordinary chronometer-escapement, the pendulum receiving an impulse only at alternate vibrations. The pendulum compensation is of steel and zinc. For adjustment of rate, I have placed a sliding-weight on the crutch-rod, where it can be moved by a nut at the level of the crutch-axis without disturbing the pendulum. I have also arranged upon the crutch-axis a peculiar apparatus (not yet tried) for adjusting the final rate of correction for temperature. At the middle of every vibration, a pin on the pendulum presses two light springs into contact, which complete a galvanic circuit; and a pin on the 60-seconds wheel interrupts the circuit once in each minute. The current thus put in motion, acting by relay, makes the seconds-punctures upon the chronograph-barrel, drives or regulates various sympathetic clocks, and in fact does all which the current from the Transit-Clock Hardy formerly did; but does it a great deal better. The steadiness of rate is very far superior to any that we have previously attained. One evidence of this is the regularity with which it indicates the barometric inequality.
As eye-and-ear observations (of circumpolar stars, &c.) are recorded by means of the transit-clock in the transit-circle-room, it is necessary to possess some means of comparing the Normal Sidereal Clock with the Transit-Clock. This is done by the contact-springs in the Transit-Clock, which are placed in connexion with the wires by which, in ordinary transits, the finger-touch causes a puncture on the chronograph-barrel; the Normal Sidereal Clock at the same time making its punctures by its own wires.
This clock was constructed, under my direction, by Messrs. E. Dent & Co, and may be regarded, I think, as an excellent specimen of horology. It was brought into use on 1871, August 21.
Other clocks have had small repairs and cleanings, requiring no special notice.
The chronograph is in good order. A small alteration has been made in its break-contact apparatus. Since 1871, October, glycerine has been used instead of water for producing the small resistances to the pendulum-movement and to the movement of the friction-regulator which are required in Siemens' Chronometric Governor; and it possesses this advantage, that it does not cause rust in the steel-work. A trifling inconvenience is produced by the absorptive power of the glycerine, which sometimes fills the cistern more than is desired.
XIII. Chronometers, Communications of Time, &c.: -
At the present time, the number of chronometers lodged in the chronometer-room is 177. Of these, 137 are the property of the Government, namely, 93 box-chronometers, 26 pocket-chronometers, and 18 deck-watches; 40 are the property of chronometer-makers, undergoing the annual competitive trial. All chronometers are compared with a Mean Solar Clock, which is sympathetic with the Normal Mean Solar Clock; some (including, among others, the chronometers on competitive trial) are compared every day, some only once in a week; all are rated for a limited time in different magnetic positions, and all occasionally in high temperatures.
Six of our chronometers were lent to the Expedition for observing the Eclipse of 1871; all are now returned.
The average excellence of the first six of the chronometers whose competitive trial terminated in August 1871 is slightly superior to that for 1870 and comparable to that for 1869.
Some time since, an accident happened to a chronometer from the weakness of the bottom of its wooden case. To prevent a repetition of this, I have had that part strengthened in all instances where it appeared advisable.
At the request of M. Quetelet, a chronometer belonging to M. Briart has been rated for several weeks. A Mean-time clock for hourly galvanic signals is now being tested preparatory to its being sent out to the Cape of Good Hope Observatory.
On 10 days, the violence of the wind has prevented the raising of the time-signal ball; but no failure has occurred from other causes.
The clock used at Deal in case of failure of the Greenwich time signal was cleaned in November last, and has performed well since. The ball was dropped by the current on 90.7 per cent. of days since the last report; on 4.9 per cent. the assistance of the attendant's hand was required; on one day the ball was not raised on account of high wind; on two occasions it was dropped a few seconds before 1h accidentally (by signals from telegraph clerks), which is notified to the public by the exhibition of a black flag; and on 3.6 per cent. communication was interrupted. In the two latter cases the ball is dropped by hand at 2h instead of Ih.
Some further correspondence with reference to the proposed establishment of a system of hourly time signals at the Start Point has resulted in a determination on the part of both the Admiralty and the Board of Trade to adhere to their former decision adverse to the proposal.
I am informed by the Engineer of the Post Office Telegraph Department that the distribution of time-signals is becoming more extensive; and a greater battery-power has become necessary at the Royal Observatory for working the additional relays at Telegraph Street.
The automatic report of the clock of the Westminster Palace shows that 60 per cent. of its errors are below 1s, 91 per cent. under 2s, and 98 per cent. under 3s.
Some of the members of the European Geodetic Association have proposed a redetermination, by galvanic signals, of the difference of longitude between the Observatories of Paris and Greenwich. I have stated my opinion that this is not desirable until chronographic registration shall be established at the Paris Observatory.
XIV.- Personal Establishment:-
The establishment of Assistants recognized in the books of the Admiralty is the same as at the last Report. The following are their names and offices:- … Mr. Ellis, Superintendent of the Time Department, and of the Money Accounts and the Stationery Stores. …
XV. Extraneous Work:-
The Total Eclipse of 1871, December, has caused no further trouble to this Observatory than that of lending instruments (sometimes requiring modifications) and chronometers, and of recovering them after use.
The preparation for the Transit of Venus, 1874, has occupied much attention. ... The first-class clocks are complete, two of the Observatory clocks being fitted with zinc and steel pendulums; nine second-class clocks are in hand, and the Observatory can furnish one. A special frame has been mounted in the lower South-East Room for attachment of the numerous clocks during their rating. We have begun to prepare skeleton forms for the calculations.
… the Report which I now offer will therefore apply to the interval between New Moon of 1872, May 7, and Full Moon of 1873, May 11.
I. Buildings and Grounds: -
Extensive repairs have been made to our telegraph-wires carried on the poles of the South-Eastern Railway, and new wires have been carried under Deptford Creek. The insulation of the wires appears to be very perfect.
Observations have been made by Mr. Hilgard, principal officer of the American Coast Survey, for determination of a fundamental longitude (as will be further mentioned); and Mr. Hilgard's transit-instrument was planted, for this purpose, in the Magnetic Court. It has been my custom, in similar instances, to fix a stone in the ground, with a short inscription, giving the name of the observer and the instrument which he has used on that spot; and I have followed this custom in the instance of Mr. Hilgard.
The preparations for the Transit of Venus in 1874 still occupy the South Ground.
The number of the erections became so considerable, far greater than could with safety or convenience be retained in the South Ground, that I was induced to solicit permission of the First Commissioner of Her Majesty's Works and Parks, for placing many of the buildings, when finished, in the Reserve Ground of Greenwich Park. The First Commissioner's consent was immediately granted, and eight of the buildings have accordingly been transferred to the Park Reserve.
V. Astronomical Instruments: -
The Sidereal Standard Clock continues to give great satisfaction. I am considering (with the aid of Mr. Buckney, of the firm of E. Dent & Co.,) an arrangement for barometric correction, founded on the principle of action on the pendulum by means of a magnet which can be raised or lowered by the agency of a large barometer.
In the galvanic relay, by which the time of the Sidereal Standard is communicated to dependent clocks or chronograph, Mr. Ellis has lately introduced large wire, with the view of avoiding the injury to the contact-springs of the clock which is usually produced by the spark when a relay of fine wire is employed.
The Clock Arnold 1 in the North Dome has been much improved by a thorough restoration of its wheel-train. It may be well now to change its gridiron pendulum for a mercurial pendulum.
The steel work of the Chronograph appears to be maintained in a bright state by the use of glycerine instead of pure water. The instrument is in good order.
XIII. Chronometers, Time Signals, Regulation of External Clocks, Operations for Longitude, &c.: -
The operations which are recorded in this Section of my Report relate almost entirely to Mean Solar Time. A sympathetic action by galvanic wires causes the indications of a small chronometer in the Computing Room to correspond exactly to those of the Sidereal Standard, and another such connexion causes the indications of another chronometer to correspond exactly to those of the Mean Solar Standard; and the Assistant in charge of time-adjustments, on whose desk these two chronometers are placed, can therefore compare, by coincidence of beats, the Sidereal Standard and the Mean Solar Standard without quitting his seat. Correcting the indication of the Sidereal Standard by means of star-transits, so as to obtain true Sidereal Time, and converting this by calculation into true Mean Solar Time, he has a comparison of true Mean Solar Time with the indication of the Mean Solar Standard, and thus he obtains the error of the Mean Solar Standard. To correct this mechanically, he puts in action (by the ordinary speaking-instrument) a galvanic current which animates a galvanic magnet in the clock-case, fixed there below a steel magnet which is carried by the pendulum of the Mean Solar Standard. With one position of the speaking-handle he introduces an attractive force which slightly accelerates the pendulum-vibrations; with the other position he produces a force which slightly retards them. The amount of acceleration or retardation for each second being known, he possesses the power, by regulating the kind and duration of connexion of the speaking-instrument, of correcting the Mean Solar Standard, even to one-hundredth part of a second of time. It is unnecessary to describe the constructions by which this Mean Solar Standard maintains the rigorous correctness of sympathetic clocks, with which chronometers are compared, or by which time-signals are disseminated or time-balls dropped, &c.
We have now in the chronometer-room 169 chronometers, whose errors and rates are ascertained by comparison with one of these sympathetic clocks. Of these, 100 box-chronometers, 15 pocket-chronometers, and 13 deck-watches, are the property of Government; 41 are the property of chronometer-makers, and are placed here on competitive trial, with the prospect of purchase to a limited extent. The Government chronometers are compared every day or every week, as appears necessary; the competitive chronometers are compared every day; and are also rated, at some time, in different positions with respect to the magnetic meridian. All chronometers are at some time rated in a temperature approaching to 100° Fahrenheit.
Among the various issues of chronometers made in the last year, by authority of the Admiralty, are 18 to the Foreign Office for use of the North American Boundary Commission, and 17 to the Challenger.
The average merit of the six first chronometers whose trial closed in 1872, August, was slightly superior to that of any preceding year. That of 1869 approached very near to it.
The rates of those chronometers are published, in a form which appears most likely to lead to examination of the causes that influence their merits or demerits. This report is extensively distributed to British and foreign horologists and instrument-makers. All these artists appear to entertain the conviction that the careful comparisons made at this Observatory, and the orderly form of their publication, have contributed powerfully to the improvement of chronometers.
On 10 days the Greenwich Time-Signal-Ball has not been raised, on account of the violence of the wind; and on one day the ball hung in its clips.
The clock at the London Bridge Station which changes the connexions of wires was cleaned and partially renovated by the S. E. Railway Company in 1872, October.
The Deal Time-Ball was not raised on 8 days, and was not dropped on 15 days, principally by the fault of a clerk. On 345 days it was dropped correctly; on 10 of these days the action of the galvanic current was assisted by a touch of the finger.
No action or correspondence has taken place with regard to the establishment of hourly time-signals on the Start Point.
Very lately, application has been made to me, through the Board of Trade, for plans and other information regarding time-signal-balls, to assist in guiding the authorities of the German Empire in the establishment of time-signals at various ports of that State. In other foreign countries (see Professor Langley in Silliman's Journal, 1872, November,) the system is extending, and is referred to Greenwich as its origin.
In Britain the demand for these signals has increased so much that a tariff of annual charges for time-signals, originating from this Observatory and circulated by the Post Office Telegraphs, is published in the' British Postal Guide,' and exhibited at some post-offices.
It seems proper now that the Observatory should be relieved from the expense attending these issues.
In the important post-office of Lombard Street, the action of a galvanic current sent from Greenwich mechanically corrects the clock. At the Westminster Palace a signal is sent from Greenwich for the guidance of the attendant. Each of these clocks automatically sends us signals to acquaint us with its state. The errors of the Westminster clock were below 1s on 67 per cent. of days, below 28 on 96 per cent., and below 3s on 99.6 per cent.
The longitude of Teheran has been determined by signals from the General Post Office. This circumstance induces me to give additional attention to the accuracy of the Mean Solar Standard Clock.
Chronographic registration having been established at the Paris Observatory, Mr. Hilgard, principal officer of the American Coast Survey, has made use of it for determining the longitude of Harvard from Greenwich, through Paris, Brest, and St. Pierre. I understand that the result does not sensibly differ from that obtained by Mr. GouId, through Valentia and Newfoundland.
XIV. Personal Establishment:-
The employments of the several Assistants may now be nearly described as follows:- ... Mr. Ellis, Superintendent of Clocks, Chronometers, Galvanic Communications, Time Signals; also of Stationery Stores, and of the Money Accounts of the Observatory. …
XV. Extraneous Work: -
In describing the preparations for the observation of the Transit of Venus, 1874, … For all the five stations I have transit-instruments, altazimuths, equatoreals, detached telescopes, and clocks, wanting only petty adjustments; and I have two photoheliographs (three more being expected in the coming summer). …
The Report, which I have the honour of laying before the Board of Visitors, refers to the period of twelve and a half lunations included between Full Moon of 1873, May 11, and New Moon of 1874, May 15, and presents the general history of the Royal Observatory during that interval, together with a statement of its condition on the last-mentioned day.
1. Buildings and Grounds: -
The only alteration of any importance in the buildings surrounding the Front Court is the inclosure of the Mean Solar Standard Clock in the Ball Lobby within double sashes, with a view to reducing the alternations of temperature to which this clock is exposed.
V. Astronomical Instruments: -
The arrangement for correction of the barometric inequality, to which I alluded last year, has been applied to the Sidereal Standard Clock with satisfactory results. The inequality is now considerably reduced; but a further adjustment of the magnets is required for its complete correction, and this is necessarily a slow process, as a long series of observations is required to determine the effect of the barometer. A uniform acceleration of rate has been shown since the clock was brought into use again (after adaptation of the apparatus) on 1874, January 24, and this has somewhat masked the barometric inequality.
The clock Hardy, which was in a bad state, has been thoroughly renovated by Messrs. E. Dent & Co., the principal alterations being the substitution of new contact apparatus and of a new escape-pinion for the old parts. While these repairs were being executed, the clock Arnold 1 was placed in the Transit-Circle-pit for use in observations of Circumpolar Stars, &c. The rate of this clock would probably be improved by the substitution of a zinc and steel pendulum (which has been found to answer so well in the Sidereal Standard and Transit of Venus clocks) for its old gridiron pendulum. This clock has now been fixed in the East Dome, where it takes the place of the clock Earnshaw, which has been lent to the Transit of Venus Expedition.
The Chronograph has worked satisfactorily throughout the past year, but will probably require cleaning before long. A pair of wires in connexion with the Chronograph is now carried to the Sheepshanks Equatoreal, and an additional pair to the Great Equatoreal.
XIII. Chronometers, Time Signals, Regulation of External Clocks, Operations for Longitude, &c.: -
There are at the present time in the Chronometer Room 194 chronometers, which are regularly rated at least once a week. Of this number, 121 box-chronometers, 14 pocket-chronometers, and 19 deck-watches are the property of the Government, and are being rated after repair by the makers preparatory to their issue to ships of H. M. Navy and 40 belong to chronometer-makers, who have placed them here for the annual competitive trial. These latter are compared every day with the Mean Solar Standard Clock; and all the chronometers are, for one or more periods of three weeks each, tried in a temperature of nearly 100° Fahrenheit. Artificial cold has not been used for any chronometer. New chronometers are always tried in different positions with respect to the magnetic meridian.
During the past year three chronometers have been transferred to the War Office, for use in the Gold Coast Expedition, and have been replaced by three others, paid for by the War Office. The number of chronometers required for the Transit of Venus Expeditions is 46; and in view of such a large demand on the ordinary stock of Government chronometers, great exertions have been made to get the repairs of chronometers (returned from service) executed by the makers with as little delay as possible.
One chronometer has been transferred to the Eastney Royal Marine Artillery Barracks, and replaced by another purchased at the same price; three chronometers, intended for the Survey of Canada, have been tried for Mr. L. Russell.
The two chronometers at the head of the competitive list for 1873 had smaller trial numbers (representing the amount of unsteadiness of rate) than any chronometer in any previous year.
With the exception of eight days, on which the violence of the wind prevented the raising of the ball, and of two days on which accidental failures occurred, the Greenwich Time-Ball has been regularly dropped every day through the year to which this Report refers.
The Deal Time-Ball was not raised on five days on account of high wind, and was not dropped on five days owing to interruption in the telegraphic communication. On one day, October 10, it was erroneously discharged four seconds before III by a telegraph-signal; on 321 days it was dropped correctly by the current; and on 37 days, principally in rainy weather, the current was too weak to release the trigger without the assistance of the attendant's hand.
A proposal has been made to me to drop a ball at Portsmouth by direct current from the Royal Observatory, but no further action appears to have been taken in the matter by the Admiralty.
Since the removal of the Telegraph Department from Telegraph Street, Lothbury, to the new building facing the General Post Office, a new and more elaborate chronopher has been constructed for the signal at 10h A.M., in which provision is made for sending signals in sixty different directions, the old chronopher being still in use for the signal at 1h P.M. Mr. H. Eaton, of the Post Office Telegraphs, has kindly furnished me with the following account of the distribution of signals:-
" The Greenwich current is received hourly. This hourly current is transmitted to 10 subscribers (mostly chronometer-makers) in London. The method of observing the current varies, and is fixed by the subscriber. In two cases, time-balls are dropped on the top of the buildings; in some other cases, model time-balls are placed in the windows; and others again use an electric bell; while two or three have a simple galvanometer, and observe from the deflexion of the needle.
The Westminster clock records its correctness and errors at Greenwich, as does also the clock at the Lombard Street Post Office.
The 10 a.m. current is most extensively used for the Provinces. It is transmitted automatically to 21 provincial towns in England (where there are subscribers), to Guernsey, Edinburgh, Glasgow, Dublin, and Belfast. In addition to the automatic sender, a sound-signal is established in the Instrument Room here; when heard, a current is sent by the clerks to over 600 offices in direct communication with the Central Telegraph Office, including the principal railway termini. Many of these offices re-distribute the time-signal to the offices radiating from them, so that practically from the 10 a.m. current from Greenwich most of the post-office and railway clocks in the kingdom are regulated.
The 1 p.m. current is transmitted automatically to nine provincial towns, viz., Newcastle, Sunderland, Middlesboro', Kendal, Hull, Norwich, Stockton , Worcester, and Nottingham. At the first four named, guns are fired; at the others, the current is observed by means of time-balls or galvanometers.
With regard to the 10 a.m. current, I should have said that there is no rule as to the method of observing; the subscribers use the form of apparatus most suitable to themselves. At the Telegraph Office the signal is recorded or observed on the telegraph instrument."
To this account it is proper to add that wire-communication has been made, experimentally, from the chronopher to the Royal Observatory, so that, by two galvanometers, the time of a current leaving Greenwich and the time of its distribution by the chronopher could be immediately compared. No sensible difference could be discovered. It follows that the hourly time-signals, based upon the most accurate determinations of time that the Observatory can furnish, may be used for accurate de terminations of longitude.
At the Lombard Street Post Office, the Greenwich current at noon starts the clock, which had stopped itself some few seconds previously, or at noon of its own time, the clock having a gaining rate. For the guidance of the attendant who regulates the Westminster clock, a signal is received at the Clock Tower from Greenwich, and a return signal is sent to the Observatory by this clock, as well as by the Lombard Street clock, to give us information as to their errors. The errors of the Westminster clock were below 1s on 67 per cent. of days, below 2s on 25 per cent., and below 3s on 5 per cent.; when the error amounts to 4s it can be corrected by the attendant, by lifting a pallet.
The rate of the Mean Solar Standard Clock seems more steady since its inclosure within double sashes.
XIV. Personal Establishment:-
The present arrangement [of the Assistants] is as follows:- ... Mr. Ellis, Superintendent of Clocks, Chronometers, Galvanic Communications and Time Signals; also of Stationery Stores, and of the Money Accounts of the Observatory. …
XV. Extraneous Work: -
Originally five [Transit of Venus] stations were selected and fully equipped with equatoreals, transits, altazimuths, photoheliographs, and clocks; but I have since thought it desirable to supplement these by two branch stations in the Sandwich Isles and one in Kerguelen's Island; and the additional instruments thus required have been borrowed from various sources, so that there is now an abundant supply of instrumental means.
The present Report refers to the condition of the Royal Observatory on 1875, May 20; and gives an account of its general transactions through the period of twelve and a half lunations, included between the New Moon of 1874, May 15, and the Full Moon of 1875, May 20 …
I. Buildings and Grounds: -
For the service of the Clock Movement of the Great Equatoreal, as will be hereafter explained, a water-cistern has been established in the highest part of the Ball-Turret, and is supplied with water by ordinary ball-service from the Kent Water Works. The height of the cistern from the ground exceeds 40 feet, but the pressure of water in the supply pipes at the ground-level is about 100 feet, and there is, therefore, no difficulty of supply. Care has been taken to increase the protection against frost, and to give means of emptying the cistern. As the rising supply-pipe passes close to the door of the Octagon Room, a hose has been laterally attached which can discharge water into the room.
V. Astronomical Instruments: -
The adjustment of the apparatus for correcting the barometric inequality of the Sidereal Standard dock appears now to be complete; and the arc of vibration is very steady.
The Chronograph is in good order, and it has not been found necessary to dean it during the past year.
Mention has already been made of the cistern in the Ball-Turret for supply of the Water-clock, the necessity for which arose from the following circumstance: - The Water-clock was supplied by a small pipe, about 80 feet in length, connected with the 3-inch Observatory main (which passes through the Park), at a distance of about 250 feet from any other branch pipe. In spite of this distance I have seen that, on stopping the water-tap in the Battery-Basement under the North-East Turret, the pressure in the gauge of the. Water-clock has been instantly increased by more than 40 lbs. per square inch. The consequent derangements of the water-clock in its now incessant daily use became intolerable. Since the independent supply was provided, its performance has been most satisfactory.
A moveable weight has been adapted to the pendulum for changing readily from Sidereal to Mean Solar time.
XV. Chronometers, Time Signals, Regulation of External Clocks: -
The number of chronometers now in the Chronometer Room is 143, consisting of l 33 box-chronometers, 3 pocket-chronometers, and 7 deck-watches. Of the box-chronometers, 49 are the property of chronometer-makers, who have placed them on the annual competitive trial; all the others are the property of the Government. The competing chronometers, and others which seem to require it, are compared with one of the sympathetic clocks of the Mean-Solar-Standard-system every day; all others every week. Every chronometer undergoes trial, at least for one period of three weeks, at temperature approaching 95°; some are exposed for cold to the open air; but no artificial cold is ever used. All new chronometers are tried with the XII. hour N, E, S, and W.
The stock of chronometers is usually kept up by purchases of the best chronometers from the competitive trial, at premium-prices submitted by me to the Board of Admiralty. Sometimes chronometers are purchased, on trial, from Navy officers. On some few occasions. (as the Chinese war) large numbers have been bought hastily; and in the spring of this year, 22 chronometers being demanded for the Arctic Expedition, 73 chronometers were immediately put on trial for selection of 22 to fill the place of those required.
One solar and one sidereal chronometer are now withdrawn from the general stock, for the service of the Observatory.
This may be a convenient place for mention of a supplemental mechanism which I have myself introduced into some chronometers. I have long remarked that, in ordinary good chronometers, the freedom from irregularities depending on mechanical causes is most remarkable; but that, after all the efforts of the most judicious makers, there is in nearly every case a perceptible defect of thermal compensation. There is great difficulty in correcting the residual fault, not only because an inconceivably small movement of the weights on the balance-curve is required, but also because it endangers the equilibrium of the balance. To remedy this, I have introduced small supplementary weights carried by means of a supplementary bar (rotating with stiff friction on the balance-staff), at whose ends are very light springs, carrying the supplementary weights, and constantly pressing them to the interior of the balance-curve. When the supplementary bar is so turned that the supplementary weights are near the end of the balance-curve, the compensation is large; when they are near the root of the balance-curve, it is small. The movement from one state to the other is so simple that probably an Assistant of the Observatory will be able to manage it; and it does not interfere with equilibrium. This arrangement has received the approval of some able chronometer-makers, and may perhaps with advantage be adopted generally.
The error-numbers of the chronometers in the competitive trial of 1874 are somewhat greater than those of several years past. The difference, however, is small; about one-tenth part of the whole.
The interruptions in the daily drop of the Greenwich Time-Ball from high wind have been only 6 in number.
The Deal Time-Ball was not raised (on account of the violence of the wind) on 5 days; and was not dropped or was erroneously dropped on 7 days, from an omission of connexion of the wires. On 45 days the current failed to release the trigger without assistance from the attendant, principally from a defect in the wire within the town of Deal, for which a new one has now been substituted. The Ball Tower at Deal has undergone some repairs.
The general system of time-signals, originating at this Observatory and disseminated by the Post-Office- Telegraph through the whole" of England, and to Scotland and Ireland, was so fully described in my last Report that I need not to enter into it further at this time. I shall only remark that the system continues to spread, and that it appears to be now a valuable National Institution.
It has been explained in former Reports that Sidereal clocks in the Observatory (as far as necessary) are connected galvanically; that all the Mean Solar clocks are connected galvanically; and that, after due comparison of clocks of the two classes, all the latter are brought to accurate time by galvanic action on the pendulum of one. Advantage is taken of the same principle when any occasional wants arise; as for hourly signals to the Magnetic Observatory, signals at every second to one of the Transit-of- Venus huts, &c.
The Lombard-Street-clock has been maintained in all the accuracy that is required for post-office purposes, with scarcely a failure; and the Westminster clock has been so well regulated, under the check of automatic report to this Observatory, that on 83 per cent. of the days of the year its error is below one second.
Proposals have been made for galvanic determination of the longitude of the Dublin Observatory, and the operation is delayed only for convenience in the arrangements to be made in Dublin.
The principal galvanic operation of the year has been, however, that connected with the Egyptian stations for the Transit of Venus. On the part external to England I shall speak hereafter; at present I allude only to the English part. By the assistance of the Post-Office, uninterrupted metallic communication was made between this Observatory and the telegraph station of the Eastern Telegraph Company at Porth Curno, a small bay a few miles east of the Land's End. Mr. Ellis proceeded to this station, carrying proper chronometers, and signals were made to and from the Observatory, and were observed at both ends. On the same evenings, signals were passed between Porth Curno and Alexandria, and were observed at both stations. These two series of observations, though made by the same person at Porth Curno, and strictly part of the flame system, were entirely independent; as, for the safety of the submarine wires, it is not considered prudent to connect them with open-air wires on land.
XVI. Personal Establishment:-
A general change in the duties of the observers has been rendered necessary by the resignation of Mr. Glaisher at the end of 1874. The actual arrangement is the following:- … Mr. Criswick, Superintendent of the Time Department generally, of Stationery Stores, and of Money Accounts. …
XVII. Extraneous Work:--
The first subject to which I have to advert is the observation of the Transit of Venus.
The parties from Egypt (A) and Rodriguez (C) are returned, with their instruments, &c.; and the instruments, &c. are returned from New Zealand (D). I am in continual expectation of the arrival of the other parties.
With regard to Egypt, the first point to be insured was the determination of the longitude of some one station. The submarine telegraph is, for commercial use, broken up into several parts. I have had experience of the troubles incident to the use of a broken line, and I determined to rely on purely astronomical methods, unless we could transmit signals in an unbroken line from Cornwall to Alexandria. This was no easy matter; the line is longer by several hundred miles than any other submarine line which has been so used; and the wire; as I understand, is smaller in section than any other long wire. I cannot say how much I am indebted to the assistance of the Eastern Telegraph Company, of their officer at Porth Curno, and of C. F. Varley, Esq., who aided us with his counsel, and who lent us (for experiment) his great resistance-apparatus, imitating the effect of a submerged wire, and other apparatus. In the actual operation, Mr. Ellis at Porth Curno received signals from Greenwich and sent signals to Alexandria; Mr. Hunter received them at Alexandria, and sent signals to Captain Orde Browne's observatory on the Mokattam Hills above Cairo (to which the Khedive had constructed a telegraph for the use of the Expedition); and communication was thus made both ways between Greenwich and Mokattam on the same night. This was repeated four times. I shall not delay further than to remark that I believe the eye-observations and the ordinary photographs to be quite successful; that I doubt the advantage of the Janssen; that one of the double-image-micrometers (an old one, very ill made, in whose construction I had no part, and which I had not seen) seems to have failed; and that the Zenith-Telescope gives some trouble. The Suez station, I expect, will wen connect us with the stations in the Indian and African seas.
The Report which I now present is intended to exhibit the condition of the Royal Observatory on 1876, May 8; and to give its general history through twelve Iunations, beginning with the Full Moon of 1875, May 20.
I. Buildings and Grounds: -
In the Battery Basement, inconvenience arose and insulation was sometimes endangered by the position of the cells of galvanic batteries upon wooden shelves. They are now all placed upon shelves of rough glass.
II. Moveable Property: -
Our astronomical instruments which were issued for use in the Transit of Venus expedition are all returned, with the exception of those that went to Kerguelen. These are still detained at Simons Town, together with some borrowed instruments, which I could much wish to restore to their owners, who so kindly acceded to applications for the loan of them.
V. Astronomical Instruments: -
The Sidereal Standard Clock is in good order.
The Chronograph has been cleaned since the last Report, and is now in excellent order. A pin lately gave way, which allowed two of the toothed wheels to separate, and the heavy weight fell; the injury to the instrument was however very trifling.
XIV. Chronometers, Time Signals, Regulations of External Clocks, Operations for Longitude: -
There are now in the Chronometer Room 161 chronometers, of which 128 are box-chronometers, 25 pocket-chronometers, and 8 deck-watches.
Of these, 47 are the property of chronometer-makers, being placed here on the annual competitive trial; the others belong to the Government, and have been either returned from service for examination and repair, if necessary, or are awaiting issue to ships of the Royal Navy after having been repaired by the maker. All such chronometers are compared at least once a week, and at some time during their period of rating are tried for at least three weeks in a temperature of nearly 100° Fahrenheit. The competitive chronometers, as well as any Government chronometers which appear to require it, are compared every day; they undergo two trials in heat for periods of four weeks each, and are also rated in different magnetic positions.
The supplementary compensation mentioned in the last Report has been applied with success to a number of chronometers, and in future all chronometers sent in to the annual trial are to be so fitted. From experiments which have been made with one of the chronometers, to which the compensation-piece has been applied, it is found that the final adjustment of the compensation can be made with certainty at the Observatory; and it will thus be unnecessary to return a chronometer to the maker, when, as has happened in a large proportion of cases lately, there is a slight error in the compensation.
The first six chronometers in the competitive trial of last year were on the average somewhat superior to those of 1874; the chronometer at the head of the list, in particular, being a very fine one.
The Greenwich Time-ball has been regularly dropped automatically on every day throughout the year, with the exception of 7 days when the violence of the wind made it imprudent to raise the ball, and of 2 days when there was accidental failure.
The Deal Time-ball was not raised (on account of high wind) on 10 days, and was not dropped orwas erroneously dropped (by telegraph signals) on 17 days. On 328 days it was dropped correctly, though on 52 of these the galvanic current was too weak to release the trigger without the assistance of the attendant, principally from the defective insulation of the wire, which has now been to a great extent overcome by increase of the battery-power.
No change has been made in the system of time-signals, which are distributed to all parts of the country by means of relay-action at the Central Office of the Post Office Telegraphs.
The regulation of the Lombard Street Clock by galvanic current from Greenwich has worked satisfactorily during the past year, and the Westminster Clock has maintained its high character, its error having been below one second on 273 days during the year to which this Report refers.
No further action has been taken in the proposed telegraphic determination of the longitude of the Dublin Observatory. Recently Prof Oppolzer has proposed to determine, by direct telegraphic communication, the longitude of Vienna, and has arranged a very complete plan of operations for this object, which I hope will be carried out shortly.
XVI. Extraneous Work:-
I first advert to the operations connected with the Transit of Venus, carrying on the history from the last Report.
The instruments also have all returned, with the exception of those from Kerguelen, which I have already mentioned as being lodged at Simons Town, At the moment of issuing this paper I learn that the Admiralty have taken efficient measures for the prompt return of these instruments.
The Report now presented gives the general history of the Royal Observatory through the period of twelve and a half lunations, comprised between 1876, May 8, and 1877, May 13, and exhibits its condition on the last-mentioned day.
II. Moveable Property: -
In our own apparatus, not included among instruments, none but the most insignificant changes have been made. …
The Astronomical instruments used for the Transit of Venus have at length been all returned from the expedition (I believe that they have not yet been fully compared, in details, with their lists); and those which had been borrowed from private contributors have been repaired, where necessary, and returned. Of those which are the property of the Government, several are lent in different directions; thus, of the five photoheliographs, one is in daily use in our own photoheliographic observatory, one is at the Cape Observatory, one at the Engineer establishment of Chatham, and one at the South Kensington Museum. The last is accompanied with Equatoreal, Transit, Altazimuth, Clocks, Micrometers, &c. with their appropriate Huts, Chemical Rooms, &c., forming a complete representation of a first-class establishment for observation of the Transit of Venus.
V. Astronomical Instruments: -
The Sidereal Standard Clock, after considerable irregularity of rate, finally stopped on January 2. It was cleaned by Messrs. E. Dent & Co., and subsequently the driving weight was slightly increased; since then the rate has been remarkably steady.
The plate-glass-cover of the Chronograph barrel was accidentally broken a short time ago. This has been restored, the instrument having sustained no injury.
XIV. Chronometers, Time Signals, Regulations of External Clocks, Operations for Longitude: -
We have now under our care 191 chronometers. Of these 34 are box-chronometers, the property of chronometer-makers, and placed here for the annual competitive trial. The others (113 box-chronometers, 26 pocket-chronometers, and 18 deck-watches) are the property of the Government, either returned from service for examination and repair, or awaiting orders for issue to ships of the Royal Navy.
The general rules for rating are these. Chronometers on competitive trial, and occasionally other chronometers (especially when a weekly rate exhibits irregularities) are compared every day with a clock sympathetic with the Mean Solar Standard Clock. Other chronometers are compared once a week. No comparisons are made in artificially depressed temperature, but every chronometer is tried in a temperature raised nearly to 100° Fahrenheit; Government chronometers at least during three weeks, competitive chronometers twice during periods of four weeks each. Competitive chronometers are also rated in four different magnetic positions. (It may be worth mention that more than a thousand chronometers have passed under my review, and that only one of these has indubitably shown signs of sensitiveness to external magnetism.) Every weekly rate is inspected by myself.
The supp1ementary compensation, to which allusion was made in the last two Reports, has now been repeatedly tried, and I think I may say that in the makers' hands it is successful. We do not doubt that chronometers are delivered to us by the makers in a better state of compensation than formerly. For the convenience of makers, it was judged prudent in the competitive trial now advancing, not to insist on the application of this apparatus to every trial-chronometer, but to intimate that the Government would be unwilling to purchase chronometers not fitted with it. More than three-fourths of the chronometers now on trial are furnished with the new supplement.
The accuracy of chronometers continues to improve, but very slowly, and not uniformly. The" trial-number," exhibiting the errors of the chronometers on the 1876 trial, referred to our usual test of the mean of the irregularities of the first six, is lower than that of any year except 1873. The first chronometer is a fine one, only surpassed in 1873.
The automatic drop of the Greenwich time-ball has failed only on 7 days when the ball was not raised on account of high wind, and on 3 days from accident. The Deal time-ball failed, on 6 days from high wind, and on 15 days from error in the telegraphic connexion; on 6 days the assistance of the attendant was required (on account of the feebleness of the current) to work the relay by which the dropping-current is created. The Lombard Street Clock has been placed under a new contract, and its action is imperfect to this extent, that it does not return signals to us. It is under the contemplation of the Telegraph Department of the General Post Office to place this clock in their general system of telegraphic time-signals, and to relieve the Observatory from all further care of it. The Westminster Clock, from some neglect of the agent of the chronometer-maker, has not fully maintained its character; it has sometimes been more than 3s in error.
Time-signals, originating at the Royal Observatory, and dispersed without sensible loss of time by the " Chronofer" of the General Post Office, are distributed, I believe with perfect accuracy, through every part of the kingdom.
In the last summer, several German gentlemen, introduced by Professor Theodor von Oppolzer, were engaged for many weeks in the time-observations and the telegraphic observations necessary for determining the longitudes of Vienna and Berlin, connected also in some measure with Munich and Paris. Under sanction of the Treasury, a temporary Observatory was provided on the Magnetic Ground. No results, I believe, were accepted by the observers, unless good transits were obtained at both ends of the line under treatment, with perfect communication on the telegraphic wire. The final results of the operation have not yet reached me.
Since the date of my last Report to the Board of Visitors, 1877, May 13, the lapse of twelve lunations leads to 1878, May 2. I am induced by this circumstance to close the present Report on May 2, describing the state of the Observatory for that day, and adverting to the transactions which have occurred between the two Reports.
II. Moveable Property: -
A large bar-magnet and a small clock which were lent to Mr. (late Sir Francis) Ronalds about thirty years since have been returned.
The Transits, Altazimuths, and Clocks employed on the Transit of Venus are stored here in an accessible state. The Equatoreals are all here, with the exception of one at the South Kensington Museum. Of the five photoheliographs: one is mounted here, and is in daily use in our heliographic observatory; one is at the Observatory of the Cape of Good Hope; one, accompanied with its special huts, &c. (but not with Transit or Altazimuth, which have been returned) at the South Kensington Museum; one is sent to the Indian Department, for observations by Colonel Tennant in India; and one is in our own shed.
V. Astronomical Instruments: -
The Sidereal Standard Clock preserves a rate approaching to perfection, so long as it is left without disturbance of the galvanic-contact springs (touched by its pendulum), which transmit signals at every second of time to sympathetic clocks and the Chronograph. A readjustment of these springs usually disturbs the rate. I contemplate the possibility of using the Standard Clock, leaving the pendulum free from the touch of springs, to give, from its wheel of 30 double-seconds, bi-secondly currents; which currents would regulate, on Mr. Jones' principle, the movement of a seconds' clock, by which the desired signals would be actually produced.
The clock" Hardy" frequently used with the Transit-Circle, had become exceedingly rusty, and has received extensive repair. The other clocks are in fairly good order.
The Chronograph required several small repairs of its wheel-work, which were effected by Messrs. Dent. It is now in good order.
XIV. Chronometers, Time Signals, Regulations of External Clocks, Operations for Longitude:-
The number of chronometers now in our hands is 178, of which 145 (107 boxchronometers,28 pocket-chronometers, and 10 deck-watches) are the property of the
Government, 4 belong to an Italian man-of-war, having been sent for a short rating, and the remaining 29 box-chronometers belong to various chronometer-makers, being placed here for the annual competitive tria1. These latter are compared daily; the other chronometers, except in special cases, only once a week. Every chronometer is tested in a temperature approaching to 100° Fahrenheit; Government chronometers for a period of at least three weeks; competitive chronometers twice for periods of four weeks each.
The supplementary compensation continues to be applied with success to Government chronometers which offer facilities for its introduction, and a marked improvement in the performance of chronometers returned after repair by the makers appears to have resulted from the increased attention now given to the compensation. Of the 29 competitive chronometers, 25 have the supplementary compensation.
In the competitive trial of last year, a slight falling off in the criterion of merit given by the mean "trial numbers" of the first six chronometers is shown, as compared with the two preceding years. The first chronometer however is a good one, fully up to the average.
A competitive trial of chronometers has been instituted at Hamburgh; and the general form of proceeding, and the arrangement of Report, are precisely copied from those at Greenwich. Reports also of a somewhat different class of time-keepers, and in a rather less elaborate form, are issued from Neufchatel.
There have only been two failures from accident in the automatic drop of the Greenwich time-ball; on 4 days the ball was not raised on account of high wind. The Deal time-ball was not dropped at 1h on 8 days, through failure of the telegraphic connexion; on 25 days the current was weak and the assistance of the attendant was required to release the trigger; on 3 days high wind prevented the raising of the ball. On the 8 days of failure of the ball-drop at 1h a black flag was hoisted, and the ball was dropped again at 2h.
The Westminster Clock was cleaned by Messrs. E. Dent & Co. last autumn, the clock being out of use from August 21 to October 11. Since this cleaning, the clock has gone with a remarkably steady rate, though sometimes affected by high wind. During the period to which this Report refers, the Westminster Clock has been 3s in error on 7 days, and 2s on 26 days. On the greater number of days the error has been under 1s.
The daily dissemination through the country of accurate time-signals, originating from this Observatory, continues to advance, without any important alteration of principle.
The present Report refers to the period of thirteen lunations from the New Moon of 1878, May 2, to the New Moon of 1879, May 20, and presents the condition of the Observatory on the last-named day.
II. Moveable Property: -
The instruments employed on the Transit of Venus remain as at the date of the last Report. The Transits, Altazimuths, Clocks, four Equatoreals, and one Photoheliograph, are stored in our shed. The Huts are lodged in the Reserve Ground of Greenwich Park.
V. Astronomical Instruments: -
No change has been made in the Sidereal Standard Clock. Arrangements are begun for regulating a clock, which should give seconds' signals on the chronograph, as mentioned in the last Report; but under the great pressure of business, they have not yet been completed.
The clock "Hardy" since its recent repairs has gone very well, and is occasionally used to mark seconds on the chronograph in case of failure in the contact springs of the Sidereal Standard. The other clocks are in good order.
The Chronograph has not required any repairs during the past year. It is in excellent condition.
XIV. Chronometers, Time-Signals, Regulation of External Clocks, Operations for Longitude: -
We have now in the Chronometer-room 167 chronometers, which are regularly rated once a week, or, in some cases, once a day. Of these 137 (93 box-chronometers, 20 pocket-chronometers, and 24 deck-watches) belong to the Government; the remaining 30 are the property of various chronometer-makers, who have placed them here for the annual competitive trial. Of the 30 competitive chronometers, 23 are fitted with my supplementary compensation.
The first six chronometers in the competitive trial of last year, show a falling off as compared with those in any of the preceding 16 years, the average "trial numbers" being taken as the test of merit.
In regard to the Greenwich Time-ball, there has been only one failure from accident in the automatic drop; on 6 days the ball was not raised on account of high wind; and on 1 day the mast was so thickly coated with ice that the ball could not be moved. The Deal ball was not dropped at 1h on 7 days, through failure in the telegraphic connexion; on 2 days the ball was accidentally dropped about 2s too soon by telegraph signals; on 17 days the current was weak, and the trigger was released by the attendant, without appreciable loss of accuracy; on the 9 days of failure of the ball-drop at 1h, a black flag was hoisted, and the ball was dropped again at 2h.
The Westminster Clock has not been quite so well regulated as usual. During the period to which this Report refers, its error exceeded 1s on 77 days; on 15 of these it was between 2s and 3s, on 4 between 3s and 4s, and on 1 day it exceeded 4s.
Prof. Oppolzer's results for the determination of the longitudes of Vienna and Berlin, made in 1877, have now been made public. They show a remarkable agreement of the Chronometric determinations formerly made with the Telegraphic. It may be of interest to recall the fact that a similar agreement was found between the Chronometric and Telegraphic determinations of the longitude of Valentia.
The dates of the Annual Reports have usually been made to depend on the limits, or on the middles, of lunations. On the present occasion the New Moon of 1880, May 9, appeared to be the most convenient day; and the entire period of the Report, extending from the New Moon of 1879, May 20, to that of 1880, May 9, is somewhat shorter than has been usual.
I. Buildings and Grounds: -
The subterranean telegraph-wires through the Park, connecting the Royal Observatory with the wires of the South-Eastern Railway, have lately become partially inefficient. The authorities of the General Post Office have been engaged in restoration of the wires; and, in furtherance of the same object, they are considering the adoption of a new line through the streets of Greenwich.
V. Astronomical Instruments: -
The Sidereal Standard Clock has not needed any repairs during the past year. Its rate has been reduced to a very small quantity by means of the sliding rate-adjuster. Experiments in applying a 2-seconds galvanic current to regulate a clock, which should give seconds' signals on the Chronograph, have been made during the last year, and, after various alterations in the regulating and regulated clocks, the results appear to be perfectly successful. It is proposed ultimately to make use of the Sidereal Standard as the regulating clock, but no alteration has yet been made in it.
The clock" Hardy" and the other clocks are in good order.
The Chronograph was cleaned last autumn, and is in excellent condition.
XIV. Chronometers, Time-Signals, Regulation of External Clocks, Operations for Longitude: -
The number of chronometers now in our hands is 229. Of these, 44 belong to various chronometer-makers, who have placed them here for the annual competitive trial; and the remaining 185 (125 box-chronometers, 32 pocket-chronometers, and 28 deck-watches) are the property of the Government. Of the 44 competitive chronometers, 11 are fitted with my supplementary compensation, and one has a palladium spring. The chronometers of all classes are ordinarily rated once a week, the competitive chronometers once a day. Every chronometer is tested in a temperature approaching to 100° Fahrenheit for one or more periods of three or four weeks each.
The competitive trial of last year shows a slight improvement on that for 1878 as regards the first six chronometers. The first chronometer is a very good one, only excelled by the first chronometer in 1873.
In connexion with the question of isochronism, observations have been made of the arcs of vibration of the balance in the case of two chronometers, which have been fitted with graduated arcs for the purpose of experiment.
There has been no failure in the automatic drop of the Greenwich Time-ball; On 4 days the ball was not raised on account of high wind. The Deal ball was not dropped at 1h on 3 days, through failure in the telegraphic connexion; on one day the ball was accidentally dropped about 4s too soon by telegraph signals, and on another day 9s too soon; on 29 days the current was weak, and the trigger was released by the attendant without appreciable loss of accuracy.
During the period to which this Report refers, the error of the Westminster Clock exceeded 1s on 120 days; on 32 of these it was between 2s and 3s, on 4 days between 3s and 4s, and on 1 day it exceeded 4s.
I have reason to believe that the use of the time-signals, originating at the Royal Observatory, and distributed automatically from the General Post Office, is becoming more and more extensive; and it seems probable that the same system may be adopted by foreign nations. Very lately an examination of our instruments was made on the part of another country, with the view of establishing something similar in one of their maritime cities; and it was intimated that Greenwich time would probably be used as standard. The establishment of time-balls, &c. at foreign ports is increasing.
In the summer of 1879 Commander Green, U.S.N., came over to this country for the purpose of determining telegraphically the longitude of Lisbon, as part of a chain of longitudes extending from South America to Greenwich. A successful interchange of signals was made with Commander Green between Greenwich and Porthcurno on four nights, 1879, June 25 to 29. The results communicated by Commander Green show that the longitude of Lisbon Observatory, as adopted in the Nautical Almanac, requires the large correction of +8.54s.
XVI. Extraneous Work:-
With regard to the Transit of 1882, I have lately placed a Memorandum before the Royal Astronomical Society. From the facility with which the requirements for geographical position are satisfied, and from the rapid and accurate communication of time now given by electric telegraph, the observation of this Transit will be comparatively easy and inexpensive. I have attached greater importance than I did formerly to the elevation of the Sun. For the four principal phases (Ingress accelerated, and retarded; Egress accelerated, and retarded) I propose to rely mainly on: 1st, the Cape Colony; 2nd, the shores of Canada and the United States, Bermuda, and the West India Islands; 3rd, the same as the 2nd; 4th, the eastern shore of Australia, or New Zealand in preference if telegraph-communication be made. I remark that it is highly desirable that steps be taken now for determining by telegraph the longitude of some point of Australia.
The present Report refers to the period of twelve and a half lunations between the New Moon of 1880 May 9, and the Full Moon of 1881, May 13, and exhibits the state of the Observatory on 1881, May 13.
I. Buildings and Grounds:-
The new line of underground telegraph-wires has been completed by the officers of the General Post Office. The new route is down Croom's Hill, joining the ordinary Post Office wires at the corner of London Street, instead of through the Circus and Circus Street' as heretofore. The result of this change, at least as regards the earth-current-wires, and probably as regards the other wires, has not been satisfactory. Allusion will be made, in a following section, to the difficulties which have been introduced. The telegraphic authorities of the General Post Office have been engaged in the search for the causes of the abnormal indications, but have hitherto found no fault in the wires. I am proceeding to change the earthplates.
II. Moveable Property:-
The only changes to record are in the disposition of the Transit of Venus instruments. Of these, three transits (to two of which, portable iron stands have been fitted by Mr. Simms), one altazimuth, and three clocks, have been sent to Mr. Gill at the Cape of Good Hope, for determination of the Cape longitude. The disposal of the other instruments remains the same as at the date of the last report:--A transit, an altazimuth, an equatoreal, and a photoheliograph, are at South Kensington; a photoheliograph is at the Cape of Good Hope; and another (telescopic part only) is in India; a photoheliograph and an equatoreal (the “Naylor”) are mounted here for daily use; and the remaining instruments, viz., one transit, three altazimuths, three equatoreals, and one photoheliograph, together with eight detached telescopes, are in our hands. In view of the Transit of Venus next year, the Corbett telescope has been adapted to the equatoreal mounting of one. of the photoheliographs, and erected for trial in the South Ground.
V. Astronomical Instruments:-
The alterations in the Sidereal Standard Clock referred to in the last report have been carried out, and it is now used to regulate, on Jones's principle, another clock placed near it in the magnetic basement. This clock in turn drives the Sidereal Relay, and, through its intermediation, registers seconds on the chronograph, and drives the system of sympathetic Sidereal clocks. For this purpose a toothed wheel has been fitted on the escape-wheel-arbor of the Sidereal Standard, giving 2-seconds' contacts by means of a pair of springs. After some difficulty occasioned by the shortness of the contact, which was met by the use of longer springs, the system has been brought into operation. The springs formerly acted on by the pendulum have been removed. As the action of the toothed wheel on the contact-springs now takes place after the impulse has been given to the pallet, and while the pendulum is quite free from the train, it is expected that the springs will not have any effect on the rate of the clock, such as was found with the former arrangement. These alterations were carried out by Messrs. E. Dent and Co., between 1880, September, and 1881, April; the clock “Hardy” being used in place of the Sidereal Standard during the interval.
The clock" Hardy" and the other clocks are in good order.
The Chronograph has been cleaned and is in excellent state.
XIV. Chronometers, Time-Signals, Regulation of External Clocks, Operations for Longitude:-
The number of chronometers now in our hands is 237. Of these, 43 belong to various chronometer-makers, who have placed them here for the annual competitive trial; and the remaining 194 (134 box-chronometers, 35 pocket-chronometers, and 25 deck-watches) are the property of the Government. Of the 43 competitive chronometers, 13 are fitted with my supplementary compensation, and one has a palladium spring. The chronometers of all classes are ordinarily rated once a week, the competitive chronometers once a day. Every chronometer is tested in a temperature approaching to 100° Fahrenheit for one or more periods of three or four weeks each. And every competitive chronometer is rated several days in positions corresponding to the four cardinal magnetic directions.
In addition to those above mentioned, 15 chronometers have been placed here on trial for the Chinese Government.
The first six chronometers in the competitive trial of 1880 were on the average, as inferred from the" “trial numbers,” slightly inferior to those of 1879, there being in particular no one chronometer of remarkable excellence. In the first few years after the strict and systematic examination of competitive chronometers, beginning with 1856, the accuracy of chronometers was greatly increased. For many years past it has been nearly stationary. I interpret this as showing that the effects of bad workmanship are almost eliminated, and that future improvement must be sought in change of some points of construction. One which occurs to me (I mention it principally as a specimen of departure from customary forms) is this. The impact of the escape-wheel upon the pallet of the balance-axis takes place very near to that axis, and must produce considerable friction, though of short duration. I proposed to the late Mr. Charles Frodsham to meet this by use of a broader pallet and a lighter impact of longer duration. The decease of that accomplished horologist prevented the completion of the trials which he had commenced for carrying out my suggestion. Other variations of the established form might be worthy of trial.
The Greenwich Time-ball has been regularly dropped automatically at 1h on every day throughout the year, with the exception of 6 days when the violence of the wind made it imprudent to raise the ball, and 8 days when the severe frost of last winter prevented its being raised; and of one day when there was accidental failure.
The Deal ball was not raised (on account of high wind) on 10 days. It was not dropped (through failure in the telegraphic connexion) on 7 days, and was erroneously dropped about 5” too soon by telegraph signals on one day; and on another day it was not dropped at lit owing to telegraph signals continuing up to 1h; on one day the current was too weak to release the trigger. On every other day the ball has been dropped automatically at 1h.
As regards the Westminster Clock, its errors have been under 1s on 31 per cent. of the days of observation, between 1s and 2s on 47 per cent., between 2s and 3s on 18 per cent., and between 3s and 4s on 4 per cent.
The distribution of time-signals to all parts of the country continues to be made on the same system as in late years, by means of the Chronopher at the Central Office of the Post Office Telegraphs. In connexion with this system, I would express the hope that the proposal to establish an hourly signal at the Start Point will be borne in mind,
Last autumn a telegraphic determination of the longitude of Leiden was made with great care by M. M. Bakhuyzen. The interchange of signals between Greenwich and Leiden occupied nearly four months. I may here remark that the American extension of longitude carried out under Commander Green, U.S.N., to which reference was made in the last Report, will be most useful for the Transit of Venus in 1882. Cannot a British officer be found to complete the operations for Australia and New Zealand? I lament that this has not been done. Mr. Gill has undertaken the necessary work for the Cape.
XVII. General Remarks:-
The present meeting may afford a fitting opportunity for the expression of my views on the general objects of the Observatory, and on the duties which they impose on all who are actively concerned in its conduct. Assuming as beyond dispute that these ought to be carried out in a spirit, liberal in itself and honorable to the nation, I proceed to state my opinion on the line of action which they suggest. …
The object prescribed to the Observatory is the promotion of “Astronomy and Navigation.” And, since the abolition of the Board of Longitude, the second of these objects (which historically gave rise to the introduction of the first) presses upon the directors of the Observatory much more strongly than before. Considering then the claims of Astronomy as bearing on Navigation, and our responsibilities in reference to them, we find that those responsibilities are by no means narrow. Whatever the rest of the scientific world may do or may not do, we are responsible for determinations of the fundamental elements of Sidereal, Solar, and especially Lunar, Astronomy, with the highest accuracy that modern skill can secure. …
The original views in making Astronomy contributory to Navigation were limited to observations of the Moon. But in the latter part of the last century, the possibility of making chronometers subservient to the determination of longitude (a subject to which the late Board of Longitude gave good attention, and to which the Government has always offered liberal rewards) was proved, and in the present century the improvement has been very great. This has been effected by our Hydrographical Office (mainly through the action of the Observatory), partly by specific rewards, partly by careful attention to the accuracy of every chronometer. purchased. And the practical value of the chronometric-system has been very greatly increased by taking advantage of the galvanic distribution of time-currents, and by the galvanic exhibition of ball-drops and other signals. There can be no doubt that all the agencies involved in this system are well employed, and that they are a legitimate part of the Observatory duty, as originally contemplated.
Still I remark that the observatory-operations bearing on chronometric navigation are not carried out to the extent which I could desire. It is known to all persons familiar with chronometers, that rates of the chronometers, obtained while the ships are actually in voyage, would possess remarkable value. We possess the power of giving facility for obtaining these, to a large part of our mercantile navy, by exhibiting a time-signal at every hour, at Deal (where the necessary apparatus already exists) and on the Start Point. I have several times brought this proposal, as regards the Start, before the Government, but unsuccessfully. But I should have. done wrong if I had omitted, in this general survey of the duties of the Observatory, to state my continued conviction that this is a proper and very desirable addition to the other points of assistance which we can give to Navigation.
Next, – closely connected, however, with the subject of Navigation, is the knowledge of the longitudes of distant ports, as referred to the Greenwich Observatory. And I approach this subject with grief. We have entirely abandoned the longitudes of the Atlantic, which have been cleared away, before our eyes, by the scientific enterprise of another nation. The Pacific, bearing those vast and important colonies, almost entirely British, is equally neglected; though so much is ready that the mission of a single officer would quickly establish all. The same aspiring nation, which has mastered the Atlantic, is now bent (as I understand) on adding to its scientific dominion the Pacific. I think this is not honorable to our nation.
The Report here presented refers to the period of twelve months ending 1882 May 20, a fixed date being taken, conveniently near to the Visitation Day.
I. Buildings and Grounds, Moveable Property, and Library;-
Of the Transit of Venus instruments, two transits, three altazimuths, five 6-inch equatoreals, two photoheliograph mountings, nine clocks, and one Transit of Venus model have been sent to Mr. Stone at Oxford for use in the forthcoming Transit of Venus, and three transits, an altazimuth, a photoheliograph, and two clocks are at the Cape of Good Hope, where they will be available for the Transit of Venus, …
II. Astronomical Observations:-
Clocks and Chronograph. – After a number of experiments in the regulation of a secondary clock by the Sidereal Standard, for registration of seconds on the chrono. graph, in which great difficulties were experienced from the shortness of the contact, the system has been given up, and since November 3 the Sidereal Standard has been used to register every alternate second directly on the chronograph, the 0s being omitted as formerly to mark the beginning of the minute. The long break of four seconds from 58s to 2s was found inconvenient, and the arrangement by which the contact was broken at the commencement of the minute has now been modified so as to give a supplementary signal through another circuit, to check the indications of the sympathetic clocks. The numeration of seconds on the chronograph is readily obtained from the signals sent in the course of each night's observations by the clock “Hardy.” The registration of each second in these signals serves as a check on the sub-division of the two seconds’ intervals into seconds. A scale has been prepared to read off the transits, and the system appears to work well.
VII. Chronometers and Time Signals:-
The number of chronometers now being tested at the Observatory is 214, 168 of which (120 box-chronometers, 23 pocket-chronometers, and 25 deck-watches) belong to the Government, and are being rated after repair previous to being issued to the Navy. The remaining 46 are placed here for the annual competitive trial, and of these 18 are fitted with Airy's supplementary compensation. In addition to the above, 6 chronometers have been placed on trial for the Mauritius Observatory, and 5 chronometers have been tested for the Japanese Government.
Notwithstanding the circumstance that the competitive trial of 1881 was more severe than usual, on account of the greater range of temperature, the first six chronometers performed on the average slightly better than those in any year since 1877, and the first chronometer was exceptionally good. The improvement shown was probably to some extent due to the. prizes offered by the Clockmakers Company, for the first time last year, for the first two chronometers.
There has been only one case of accidental failure in the automatic drop of the Greenwich time-ball. On 4 days the ball was not raised on account of the violence of the wind.
The Deal ball has been dropped automatically at 1h on every day throughout the year, with the exception of 15 days, on which there was either failure in the telegraphic connexion or interruption from telegraph signals continuing up to 1h, and of one day when the current was too weak to release the trigger without the attendant's assistance. On 3 days high wind made it imprudent to raise the ball.
The Westminster Clock has continued to perform well, its errors having been under 1s on 40 per cent. of the days of observation, between 1s and 2s on 44 per cent., between 2s and 3s on 14 per cent., and between 3s and 4s on 2 per cent,
Time-signals, originating in the Observatory, are distributed at l0h a.m. and 1h p.m. to all parts of the country by the Post Office Telegraphs.
The period to which the present Report refers comprises the twelve months ending 1883 May 20.
I. Buildings and Grounds, Moveable Property, and Library:-
The instruments purchased for the Transit of Venus 1874, after being used for the observation of the Transit of Venus 1882, have for the most part been returned to the Observatory. We have now in our hands one transit, two altazimuths, five equatoreals, one photoheliograph (mounted for daily use), and the mounting of another to which the Corbett telescope has been adapted. Three transits, one altazimuth, and one photoheliograph are at the Cape; two photoheliograph mountings (to which 6-inch object glasses have been applied) and a photoheliograph tube have been lent to the Eclipse Expedition 1883; a transit and an altazimuth have not yet been returned after observation of the Transit of Venus in Brisbane. The”Naylor” equatoreal, an altazimuth, and a clock (Dent 2015) were lost in the wreck of the “City of Brussels” on the voyage back from Bermuda.
Of the remaining clocks, four have been returned, one (Dent 1914) was presented to the Khedive after the Transit of 1874, and six are still in the charge of the Transit of Venus (1882) Committee. A photoheliograph tube is at South Kensington and another is in India.
II. Astronomical Observations:-
Clocks and Chronograph. – The system of registering the alternate seconds from the Sidereal Standard directly on the chronograph has been continued, and is found perfectly satisfactory. The Sidereal Standard has been recently cleaned.
VII. Chronometers and Time Signals:-
The number of chronometers now being tested at the Observatory is 154. Of these 114 (77 box-chronometers, 16 pocket-chronometers, and 21 deck-watches) are the property of the Government and are being rated after repair previous to their issue to-the Navy. The remaining 40 are placed here for the annual competitive trial, and of these 8 are fitted with Airy's supplementary compensation. In addition to the above, 5 chronometers have been tested here for the new Hong Kong Observatory.
The first six chronometers in 1882, as tested by their trial numbers, are on the average better than the first six in any year since 1873, and the first chronometer performed better than any we have had previously on trial. The trial in cold was, however, not quite so severe in 1882 as in preceding years.
There has been no case of failure in the automatic drop of the Greenwich time-ball. On three days the ball was not raised on account of the violence of the wind.
The Deal time-ball has been dropped automatically at 1h on every day throughout the year, with the exception of 5 days, on which there was failure in the telegraphic connexion, of one day when the ball was accidentally dropped 4s too soon by telegraph signals, and of 14 days when the current was weak and the trigger was released by the attendant without appreciable loss of accuracy. On12 days the ball was not raised on account of the violence of the wind.
Mr. Leonard has expressed a wish to make other arrangements for the dropping of the Deal ball, as he proposes to use for another purpose the wire from Greenwich to London Bridge, by which time signals are sent to the South-Eastern Railway and the Deal ball is dropped independently of the signals sent to London by the Post Office wire. It has been ascertained that the Deal ball could be dropped through the Post Office connexions and a return signal to Greenwich given, but no further step in the matter has yet been taken.
The Westminster Clock has maintained its high character, its errors having been under 1s on 66 per cent. of the days of observation, between 1s and 2s on 25 per cent., between 2s and 3s on 6 per cent., and between 3s and 4s on 3 per cent. The error has never exceeded 4s.
The present Report refers to the period of twelve months from 1883 May 21 to 1884 May 20, and exhibits the state of the Observatory on the last-named day.
1. Buildings and Grounds, Moveable Property, and Library: -
The instruments lent to the Transit of Venus Committee have all been returned, with the exception of a clock (Dent 1915) which has been sold to the Natal Observatory, and of the instruments lost in the wreck of the “City of Brussels.” A 6-inch equatoreal by T. Cooke and Sons has been transferred to the Observatory by the Transit of Venus Committee, with the sanction of the Treasury, to replace the Naylor equatoreal. Of the instruments purchased for the Transit of Venus 1874, there are now at the Observatory two transits, two altazimuths, five 6-inch equatoreals, and two photoheliographs, one of which is mounted for daily use. Three transits, an altazimuth, and a photoheliograph are at the Cape; one photoheliograph and the mounting of another are at South Kensington, and a photoheliograph tube is in India. An altazimuth has been lent to the Observatory of the Royal Naval College, and the 6-inch object-glass of the Hodgson equatoreal has been temporarily lent to the Experimental Light Committee of the Trinity House. The two 4-inch telescopes lent to Captain Wharton, R.N., have been returned.
II. Astronomical Observations: -
Clocks and Chronograph. – The mean solar clock, made many years ago by Shepherd and Son, has on several occasions in the past year stopped through failure in the electric contact made by the pendulum. Mr. Shepherd has proposed an improved form of electric escapement, which he has fitted to a pendulum to be placed here for experiment within the next week. Meanwhile, in order to avoid the inconvenience caused by the stopping of the mean solar clock, which sends out the hourly time-signals to the Post Office for general distribution, one of the Transit of Venus clocks (Dent 2012) has been fitted by Messrs. E. Dent and Co., with the requisite contact springs, so that it can be used at any time in place of the electric mean solar clock, and a relay adapted for driving the sympathetic clocks by means of the clock Dent 2012 is being made.
VII. Chronometers and Time Signals: -
The number of chronometers now being tested at the Observatory is 192, and of these 155 (115 box-chronometers, 17 pocket-chronometers, and 23 deck-watches) belong to the Navy, 33 are placed here for the annual competitive trial, and 4 are on trial for purchase by the Austrian Government.
The first six chronometers in the competitive trial of 1883 were slightly above the average of recent years as inferred from the trial numbers.
No failure in the automatic drop of the Greenwich time-ball has occurred during the year to which this Report refers. The ball was not raised on two days on account of the violence of the wind, and on four other days during the repair of the machinery.
As regards the Deal time-ball, after various delays the arrangement, referred to in the last Report, for sending a current to Deal and receiving a return-signal through the Chronopher of the Post Office telegraphs, was brought into operation on February 29, and has worked well since. The change has necessitated some slight alteration in our arrangements in order that we may be able to receive the Westminster signal through the same wire which is now used for the Deal current and its return signal. There have been 16 cases of failure in the dropping of the Deal time-ball owing to interruption of the telegraphic connexions, 12 under the old system, and 4 since the new arrangement with the Post Office. On 19 days the current was weak and required the assistance of the attendant to release the trigger, and on 9 days the violence of the wind made it imprudent to raise the ball.
The errors of the Westminster Clock have been under 1s on 53 per cent. of the days of observation, between 1s and 2s on 30 per cent., between 2s and 3s on 13 per cent., between 3s and 4s on 3 per cent., and between 4s and 5s on 1 per cent.
THE Report here presented refers to the period of twelve months from 1884 May 21 to 1885 May 20, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library: -
The work of connecting the drainage of the Observatory with the Main Drainage System has now been completed by the Director of Works' Department. It is intended to lay a drain to carry away the waste water from the sink in the Magnet basement, and I propose to take advantage of the opening of the ground to lay a line of pipes underground for the ventilation of the basement by air which has acquired the temperature of the soil at a depth of several feet below the surface. It is hoped that by this means greater uniformity of temperature may be maintained in the Magnet basement.
As regards moveable property, three transits, an altazimuth, and a photoheliograph are at the Cape Observatory; a photoheliograph and the mounting of another are at South Kensington. the photoheliograph tube being in India; a transit, an altazimuth, and the Simms 6-inch equatoreal No. 2 have been lent for exhibition at Bethnal Green Museum; an altazimuth and the Lee 6-inch equatoreal have been transferred to the Royal Naval College and to the Hong Kong Observatory respectively; the Hodgson 6-inch object-glass is in the hands of the Elder Brethren of the Trinity House for photometric experiments; a photoheliograph mounting has been lent to the Mountain Observatory Committee of the Royal Society; and a clock (Dent 2011) is at present at Kew Observatory.
II. Astronomical Observations: -
Clocks and Chronograph. – The Sidereal standard clock was cleaned at the beginning of April. The Ohronograph has required extensive repair, the train of wheels having become much worn in course of years. Various improvements suggested by experience have been carried out by Messrs. E. Dent and Co., and the instrument appears now to be in very good order. The chronograph was out of use for two and a half months, during which time the transits were observed by eye-and-ear.
On Jan. 1 the public clock at the Observatory entrance and the other mean solar clocks were put forward 12 hours so as to show Greenwich civil time, starting at midnight and reckoning from 0h to 24h, which would correspond with the Universal time recommended by the Washington Conference. The change from astronomical to civil reckoning has also been made in all the internal work of the Observatory, and has been carried out without any difficulty. Greenwich civil time is found to be more convenient on the whole for the purposes of this Observatory, but its introduction into the printed astronomical observations has been deferred to allow time for a general agreement amongst astronomers to be arrived at. It is proposed, however, to adopt the civil day without further delay in the printed magnetical results, thus reverting to the practice previous to 1848, and making the timereckoning harmonize with that used in the meteorological results, the reckoning from 0h to 24h being for the future adopted in both cases.
VII. Chronometers and Time Signals: -
The number of chronometers now being tested at the Observatory is 151, and of these 103 (79 box-chronometers, 13 pocket-chronometers, and 11 deck-watches) belong to the Navy, 40 are placed here for the annual competitive trial, and 8 are on trial for purchase by the Austrian Government.
The first six chronometers in the competitive trial of 1884 were rather above the average of the last ten years as inferred from the trial numbers. As much difficulty is experienced in maintaining the chronometer oven at a nearly constant temperature, an apparatus has been procured from Mr. Kullberg which is designed to effect this automatically, by the action of a compensation-bar, which, as the temperature rises, gradually closes a small hole through which the supply of gas to the gas burners passes. The apparatus has not yet been brought into use, as the chronometer oven has been constantly required for testing chronometers since it has been received.
The automatic drop of the Greenwich time-ball failed on 6 days through the clock-train stopping. The ball was not raised on 3 days on account of the violence of the wind.
As regards the Deal time-ball, which is now dropped by current passing through the chronopher of the Post Office telegraphs, there have been 14 cases of failure owing to interruption of the telegraphic connections, and on one day the current was too weak to release the trigger without the assistance of the attendant.
In connection with the establishment of hourly time-signals at the Start or Lizard, which was long advocated by Sir G. B. Airy, I have received from the Committee of Lloyds', in answer to my inquiry, an assurance that that corporation would be willing to undertake the maintenance of hourly time-signals at any of their signal stations, provided the Government would supply the necessary apparatus. After consultation with Capt. Wharton, it has been thought better that, before taking further steps, some preliminary trials should be made of a collapsible cone as an hourly time-signal, facilities for doing which exist at Devonport. As regards balldrop or other time-signal, I would propose that it should be made automatically by a local clock, to be corrected daily by the help of a time-signal from Greenwich at 10 a.m., which should automatically start an auxiliary seconds’ pendulum, suspended freely just behind the clock pendulum. The attendant would then accelerate or retard his clock pendulnm [pendulum] (by electro-magnetic action as in the Greenwich mean solar clock) so as to make it pass through the middle of its vibration at the same time and in the same direction as the auxiliary pendulum, and thus to indicate accurately Greenwich mean time. A return signal to Greenwich sent by the local clock at the next hour (11 a.m.) would show that this clock had been properly corrected, and would be a guarantee for the general accuracy of the time-signals. Preliminary trials have shown that the observation of coincidence of vibration of two pendulums Can be made with great certainty, and Messrs. E. Dent and Co. are now arranging for the mounting of an auxiliary pendulum on one of the Transit of Venus clocks [Dent 2010], and for adapting it to give hourly time-signals.
The errors of the Westminster Clock have been under 1s on 50 per cent. of the days of observation, between 1s and 2s on 29 per cent., between 2s and 3s on 10 per cent., between 3s and 4s on 7 per cent., and over 4s on 4 per cent.
THE Report here presented refers to the period of twelve months from 1885 May 21 to 1886 May 20, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
As proposed in the last Report a line of 9-inch pipes about 155 feet in length has been laid underground for the ventilation of the Magnet basement, the depth below the surface varying from 5 feet at the lower end in the South Ground to 11 feet 6 inches at the entrance to the basement. Thus the air which is admitted (by means of two branch pipes) into the east and west arms of the basement is warmed in winter and cooled in summer by passage through a considerable extent of soil at nearly constant temperature. A drain for carrying away the waste water used in the photographic operations is laid below the line of ventilating pipes, the latter being carefully isolated from the drain pipes.
A portable electric lamp has been purchased for use in examining the interior of clocks and in spectroscopic observations.
II. Astronomical Observations:-
Clocks and chronograph. – The rate of the Sidereal standard clock was much affected by exposure to cold in the course of the work on the ventilation and drain pipes in the Magnet basement, but the clock has gone very steadily since, and it has therefore been thought better not to clean it at present. The chronograph has required cleaning three times since the date of last Report.
A clock synchronized by hourly currents, on Lund's system, has been presented to the Observatory by the Standard Time and Telephone Co., and is fixed in the Astronomer Royal's Office.
VII. Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers now being tested at the Observatory is 115, and of these 81 (59 box-chronometers, 9 pocket-chronometers, and 13 deck-watches) belong to the Navy, the remaining 34 being placed here for the annual competitive trial. The number of chronometers entered originally for this year's trial was 37, but three of these, which had taken a high place in last year's trial, were purchased by the Admiralty in February, and consequently withdrawn from the trial.
The first six chronometers in the competitive trial of 1885 were slightly below the average of the last ten years, as inferred from the trial numbers.
Mr. Kullberg's apparatus for automatically regulating the temperature of the chronometer oven has been in use since last November, and is perfectly successful in maintaining the temperature constant within narrow limits. A double casing packed with a non-conducting material (slag-wool) has been applied to the sides and top of the chamber, and this is found to contribute materially to constancy of temperature in the oven.
As the termination of the annual trial falls at an inconvenient part of the financial year for the purchase of chronometers, it has been decided to make the trial commence in future on the first Saturday in July, so that it would end in the latter part of January. The temperature conditions in the room will be practically the same as at present, but in reverse order, commencing with warm weather and ending with cold. The rating is to be for 29 weeks, viz., three periods of 7 weeks each in the room and two periods of 4 weeks each in the oven.
It is proposed also to have an annual trial of deck-watches for purchase by the Admiralty. The first trial is to commence on November 27 this year, and end on 1887 January 22; the deck-watches to be tried for two periods of 2 weeks each in the room at a mean temperature of 50° to 55°, and for one period of four weeks in different positions in the oven at a temperature of about 85°.
The automatic drop of the Greenwich time-ball failed on 2 days during the past twelve mouths, on one occasion through accumulation of snow on the mast, and on another through failure in the clock-work apparatus for daily. reversal of the currents through the electro-magnets. This apparatus has since been removed, and the direction of the currents is now reversed by hand once a week. On one day the ball was not raised on account of the violence of the wind.
As regards the Deal time-ball, there have been 7 cases of failure owing to interruption of the telegraphic connections, and on 3 days the violence of the wind prevented the raising of the ball. There have been three cases of failure of the 1 p.m. signal to the Post Office.
No further action has been taken as regards. the establishment of hourly time-signals at the Lizard or Start, as the arrangements for preliminary trial of a collapsible cone at Devonport are not yet completed. One of the Transit of Venus clocks (Dent 2010) has been adapted by Messrs. E. Dent and Co. to give hourly time-signals, and to be synchronized by the help of an auxiliary seconds' pendulum on the plan I proposed in the last Report.
The contact apparatus of the Westminster Clock having been out of order, no signals have been received during the past twelve months. New contact apparatus of improved construction is now being fitted.
The longitude of Gibraltar was determined last year under Capt. Wharton's direction, by exchange of telegraphic signals on August 8, 9, and 12 between Greenwich and Gibraltar, the Eastern Telegraph Co. having courteously given the free use of their telegraph cable for the purpose. The signals were transmitted by relay-action from the ends of the cable to the observing stations at Greenwich and Gibraltar. Local time was determined at Gibraltar by the officers of H.M.S. " Sylvia" with the sextant, and at Greenwich by Commander Moore and Lieut. Douglas by means of sextant observations, and also by transits with the transit-circle. In connection with this determination a large number of observations of signals were made at Greenwich for determination of the personal equations of the different observers in observing telegraph signals. At Greenwich the longitude signals were observed by five observers independently. Commander Moore and Lieut. Douglas made a series of observations at Greenwich last summer for comparison of the relative value of determinations of local time made with a sextant and with a small transit instrument respectively.
IX. General Remarks:-
Commencing with the year 1885, Greenwich civil time, reckoning from midnight to midnight and counting from 0 to 24 hours, has been adopted in the Spectroscopic and Photographic Results as well as in the Magnetical and Meteorological. It is proposed to defer the introduction of this time-reckoning into the Astronomical Results till the year 1891, for which year the Board of Visitors have recommended its adoption in the Nautical Almanac. In an Observatory such as this, where observations of various classes are carried on, there is, however, considerable inconvenience in the retention of the present astronomical day, which now involves the use of two systems of reckoning mean solar time in the same establishment.
The present Report refers to the period of twelve months from 1886 May 21, to 1887 May 20, and exhibits the state of the Observatory on the last-named day.
1. Buildings and Grounds, Moveable Property, and Library:-
As regards moveable instruments, three transits, an altazimuth, a photoheliograph, and two clocks (Dent 1916 and 2013) are still at the Cape Observatory, a photoheliograph and the mountings of two others (without the tubes) are at South Kensington; a photoheliograph tube is in India; a transit, an altazimuth and a 6-inch equatoreal (Simms No. 2) have been lent for exhibition at Bethnal Green Museum, an altazimuth has been transferred to the Royal Naval College, and the Lee 6-inch equatoreal to the Hong Kong Observatory, the Hodgson 6-inch object glass is still in the hands of the Elder Brethren of the Trinity House for photometric experiments, and a clock with zinc and steel pendulum (Dent 2011) has been lent to the Kew Observatory. …
The old instruments and apparatus stored in the South-east lower room have been thoroughly overhauled by Mr. Lewis, and those that appeared to be merely of historical interest have been transferred to Library 4, under the Altazimuth dome. The remainder are now disposed so as to be readily available for use.
II. Astronomical Observations:-
Clocks and Chronograph. – Several auxiliary clocks which had not been cleaned for many years have been cleaned recently. The sidereal standard and mean solar clocks and the chronograph are in good order.
VII. Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers now being tested at the Observatory is 225, and of these 170 (126 box-chronometers, 19 pocket-chronometers, and 25 deck-watches) belong to the Navy, 52 box-chronometers are the property of various chronometer makers, who have sent them for the special competitive trial, and 3 deck-watches have been placed here for trial by Messrs. E. Dent & Co., with a view to the selection of 2 of them to be transferred to the Navy in exchange for some old chronometers.
The first seven chronometers in the competitive trial of 1886 were exceptionally good, the first chronometer being superior to any we have previously had on trial, except the first in 1882.
As mentioned in the last Report, the time of commencement of the annual trial of chronometers has been altered to the first Saturday in July, so that the trial may terminate at a time more convenient for the financial arrangements of the Admiralty.
But as it is desired to increase the stock of Navy chronometers without delay, a supplementary trial (for which 52 chronometers have been entered) was commenced on March 5, the rating to terminate on June 18, just before the commencement of the ordinary annual trial.
For the annual trial of deck-watches, which commenced last November, 15 watches were entered, and of these 9 were purchased for the Navy, the first three being classed "A," or equal, in performance, to an average box-chronometer.
A supplementary trial took place in February and March, for which 9 deck-watches were entered, and of these 7 were purchased for the Navy, the first two being classed "A."
The watches in each trial were rated for a period of 9 weeks, viz., 2 weeks (dial up) in the room at a temperature of 50° to 55°, 4 weeks in four different positions in the oven (dial up, pendant up, pendant right, pendant left, arranged symmetrically) at a temperature of about 80°, and 3 weeks (dial up) in the room. When the period of rating in any position was less than a week, weekly rates were inferred from the rate for the period by simple proportion.
In order to compare the performances of the several watches, "trial numbers," representing deviations in weekly rates, have been formed on the same general principles as for the chronometer trials. The trials in different positions introduce, however, a new element, and an arbitrary weight must be assigned to them in combining them with the trials "dial up." It has been considered that when the watch is worn in the pocket the pendant will generally be "up," and that not more than one-third of the deviation" pendant right" or "pendant left" is likely to have practical effect.
Putting
a = Difference between greatest and least weekly rates "dial up,"
b = Greatest difference betweeb one week and the next "dial up,"
c = Difference between weekly rates "pendant up" and "dial up,"
d = Difference between weekly rates "pendant right" and "dial up,"
e = Difference between weekly rates "pendant left" and "dial up,"
the quantity c + d/3 + e/3 may be taken as the measure of deviation in weekly rate due to positions in ordinary wear. Half weight has been given to this quantity in combining it with the trial number "dial up" (a +2b), on the assumption that the deck-watch would be usually lying "dial up" and that it would not be carried in the pocket more than eight hours a day on average.. Thus the quantity a +2b +1/2(c +d/3 +e/3). has been adopted as the trial number for deck-watches. It has been arranged that for the future all pocket chronometers and deck-watches rated at the Observatory after repair shapp be tested in positions.
The collowing is a statement pf the trials of chronometers and deck-wathces for purchase from the beginning of 1886 to the present time:-
| Annual trial of 37 chronometers for the Navy | from 1886 Jan. 9 to 1886 July 24. | |
| Trial of 15 deck-watches for the Navy | from 1886 Feb. 15 to 1886 Mar 6. | |
| Trail of 2 chronometers for teh Navy | from 1886 July 10 to 1886 Nov. 6. | |
| Trail of 8 chronometers for the Indian Gvovernment | from 1886 Sept. 1 to 1886 Sept. 31. | |
| Trail of 4 deck-watches for the Indian Gvovernment | from 1886 Sept. 1 to 1886 Sept. 31. | |
| Trial of 15 deck-watches for the Navy | from 1886 Nov. 27 to 1887 Jan. 22. |
|
| Supplementary trial of 9 deck-watches for the Navy | from 1887 Feb. 5 to 1887 April 2. | |
| Supplementary trial of 52 chronometers for the Navy | from 1887 March 5 to 1887 June 18. |
|
| Trial of 3 deck-watches for the Navy | from 1887 May 16 to 1887 July 18. |
In addition to the above, 3 chronometers have been tested for the Indian Government after being repaired.
The temperature of the chronometer oven has been successfully regulated by Mr. Kullberg's automatic apparatus to the temperature of about 80° for the trials of deck-watches as well as to the higher temperature at which chronometers are tested.
In June and July last year, Mr. Lewis spent several days at the Admiralty in comparing the chronometer books kept there with those of the Observatory, and after some trouble a complete accordance was finally secured.
The automatic drop of the Greenwich time-ball failed on one day only during the past twelve months. On three days the ball was not raised on account of the violence of the wind, and on five days on account of accumulation of snow on the mast.
As regards the Deal time-ball, there have been twelve cases of failure owing to interruption of the telegraphic connections, and on three days the violence of the wind prevented the raising of the ball. For fourteen days after the snow storm of December 26-27, no signals were sent to or received from the Deal time-ball tower, telegraphic communication being interrupted. There have been four cases of failure of the 1 PM. signal to the Post Office Telegraphs.
The arrangements for hourly time-signals at Devonport to be given by a local clock, corrected daily by the help of a time-signal at Greenwich at 10 A.M., have been
carried out under Captain Wharton's directions, and a return signal from Devonport (serving as a test of the accuracy with which the local clock was corrected) has been regularly received at Greenwich (at 13h 0m 39s G.C.T.) since November 22, with the exception of 36 days following the snowstorm of December 26-27, when there was interruption of the telegraphic communication with the west of England, and of 23 days when no return signal was received. The failures occurred for the most part on Sundays. The plan appears to answer well, and it seems desirable that apparatus should be provided by the Government to enable the Committee of Lloyd's to establish hourly signals at the Lizard on the same system.
The new contact apparatus of the Westminster clock was brought into action on 1886 May 22, and the automatic signals from the clock have been received regularly from that date, except on three days following the snowstorm of December 26-27. The error of the clock was insensible on 25 per cent. of the days of observation, 1s on 40 per cent., 2s on 22 per cent., 3s on 11 per cent., and 4s on 2 per cent. On one day the signal was 15s late and on another day 10s late.
A suggestion has been made that in view of the importance of the connection of the British and Continental surveys, the telegraphic difference of longitude between Greenwich and Paris, which was originally determined with great care in 1854, should be confirmed in order to complete the network of telegraphic longitudes which have been determined of late years by continental astronomers. It seems desirable that Greenwich Observatory, which, under Sir G. B. Airy's direction, took such an active part in utilizing the telegraph for the determination of longitude should now assist in completing the cycle. The necessary exchange of observers and signals could conveniently be carried out in the summer of next year, when the French geodetists will, I understand, be prepared for their share of the work.
IX. General Remarks:-
The appointment of a clerk, which has presumably received the sanction of the Admiralty, will, when it is made, provide for the increase of office-work which has taken place of late years in regard to chronometers, accounts, stores, stationery, printing, &c" and if the maintenance of the telegraph wires, batteries, &c., for communication of time-signals were undertaken by the Post Office Telegraphs as part of the distribution of time to the public, there would be some further relief. But to enable me to give time to extraneous questions referred to the Astronomer Royal by the Government, it appears necessary that the Chief Assistant and I should be relieved of certain mechanical work which might be entrusted to computers, and that further responsibility should be delegated to the Assistants. Proceeding on the lines which have been laid down by my predecessor, I believe that the maximum of efficiency at the minimum of cost would be attained if an increase of work were met by an increase in the staff of computers, with due recognition of the position of two or three senior computers, and of the increased responsibility of the Assistants.
The Report here presented refers to the period of 356 days from 1887 May 21, to 1888 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
As regards moveable instruments, three transits, an altazimuth, a photoheliograph, and two clocks (Dent 1916 and 2013) are at the Cape Observatory; a photoheliograph and the mountings of two others (without the tubes), an equatoreal (Simms' No. 2), a transit, and an altazimuth have been lent to the Science and Art Department, the three last-named for exhibition at Bethnal Green Museum; a photoheliograph tube is in India; an altazimuth has been transferred to the Royal Naval College and the Lee 6-inch equatoreal to the Hong-Kong Observatory, and a clock (Dent 2011) is at Kew Observatory. The Hodgson 6-inch object glass, lent to the Elder Brethren of the Trinity House for photometric experiments, and the micrometer for measuring the Transit of Venus photographs, lent to Capt. Darwin, have been returned. The telescope of the Simms' equatoreal No. 1 and a small portable equatoreal mounting were used by Mr. Turner for observations of the Solar Eclipse of August last in Russia. …
II.-Astronomical Observations:-
Clocks and Chronograph. – These are all in good order. The Sidereal Standard stopped on October 15, through thickening of the oil. It was cleaned by Messrs. E. Dent & Co., and brought into use again on November 7.
V. Meteorological Observations:-
The driving clock of the new thermograph had, as mentioned in the last Report, given much trouble, and was eventually sent to Mr. Kullberg in May 1887 for improvement of the mechanism. Many small changes were made and a new pendulum was provided. The new thermograph was brought into use again on Oct. 11, the old thermometer apparatus, which has not been dismounted, being used in the interval.
VII. Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers now being tested at the Observatory is 154 (111 box chronometers, 19 pocket chronometers, and 24 deck watches), all of which belong to the Navy. The chronometers for the annual competitive trial, which is now held in the latter half of the year, will not be deposited at the Observatory till June 18.
In the year 1887 the average daily number of chronometers being regularly rated was 224, the total number of chronometers received was 717, the total number issued was 642, and the number sent for repair was 315.
Since the date of the last report two competitive trials of chronometers and the annual trial of deck watches have been completed, besides a trial of ten chronometers for the Austrian Government. In the supplementary trial of chronometers, terminating in June last, the first seventeen chronometers were all good and the general standard of excellence was very high, though the somewhat shorter duration of the trial prevents a strict comparison of trial numbers with those in the annual trials. The first chronometer in the annual trial, 1887, was very good indeed, and the next four appear to be fine chronometers. The performance of the first six was decidedly above the average of recent years, though the trial was somewhat more severe than usual as regards range of temperature, the extremes being 37° and 100°Fahrenheit.
For the annual trial of deck-watches, 1887 Nov. 26 to 1888 Feb. 11, 21 watches were entered, and of these nine were purchased for the Navy, the first three being classed "A" or equal in performance (on the 11 weeks' trial) to an average box chronometer.
All pocket chronometers and deck-watches on trial for the Navy, whether for purchase or after repair, are now tested in different positions as well as in the oven.
At Capt. Wharton's request some experiments were made in the latter part of 1887 on a chronometer, the rate of which appeared to be affected by the motion of the ship. It was found that the rate of this chronometer. with the gymbals free was different from that with the gymbals fixed, two other chronometers which were tested in the same way for comparison showing no such defect.
In March and April the chronometer books kept at the Admiralty were again compared with those of the Observatory, and the discrepancies rectified.
There has been no failure in the automatic drop of the Greenwich time-ball, but on four days the ball was not raised on account of the violence of the wind.
The automatic drop of the Deal time-ball failed on six days owing to interruption of the telegraphic connections, and on two days high wind prevented the raising of the ball. There has been no case of failure of the 1 p.m. signal to the Post Office Telegraphs.
The return signal from the Devonport time-ball clock (corrected daily by the help of a time-signal from Greenwich) failed on 30 days, 7 of these being Sundays. The apparent error of the signal was under 0.2s on 72 per cent. of the days of observation, under 0.5s on 88 per cent., between 0.5s and 1.0 s on 9 per cent., and exceeded 1s on 3 per cent. It seems probable that on several of the days when the error exceeded 1s a false signal was observed. A monthly report of the observed times of the return signals is now forwarded regularly to the Hydrographer, and a telegram is at once sent to Devonport whenever the signal is 0.5s or more in error.
There have been 23 failures in the automatic signals from the Westminster clock since the date of the last Report. The error of the clock was insensible on 25 per cent. of the days of observation, 1s on 38 per cent., 2s on 20 per cent., 3s on 15 per cent., and 4s on 2 per cent.
Provision has been made in the estimates for the expense of a re-determination of the difference of longitude between Greenwich and Paris, and I have been in correspondence with the French authorities on the subject. The regretted death of General Perrier occurred before any definite plan had been settled, but his successor, M. le Commandant Bassot, has taken the matter up warmly in concert with Admiral Mouchez, and the French Bureau des Longitudes has approved the scheme, which is to include a determination of the longitude of Dunkirk. Three French delegates (M. Loewy, M. Bassot, and M. Defforges) propose to visit Greenwich very shortly to settle the details of the plan of operations which it is intended to carry out in the autumn. In preparation for the work, Mr. Turner and Mr. Lewis have observed for practice, by eye and ear, a number of galvanometer signals sent by another observer and automatically registered on a chronograph, 5 sets of 10 signals having been recorded on each of 7 days.
IX. General Remarks:-
Allusion was made in the last report to the increased demands made on the Observatory in recent years both by the scientific and the general public, and in view of the consequent development of work it now becomes necessary to review the position of the establishment, which was constituted many years ago, when the conditions were very different. In order to understand the difficulty of the present situation it is necessary to bear in mind the following facts:- In 1835 there were 5 Assistants (excluding the Chief Assistant) having no computers to superintend, no extraneous work beyond the care of a relatively small number of chronometers for the Navy, no magnetic and meteorological observations, no altazimuth observations, no spectroscopic and photographic observations. At the present time there are 8 Assistants (excluding the Chief Assistant) having 15 computers to superintend, and of this staff two Assistants are absorbed by the Magnetic and Meteorological Branch, one by the Altazimuth, and two by the Spectroscopic and Photographic Branch, leaving only three Assistants to do the Astronomical work, which in 1835 required five Assistants, and in addition to perform all the extraneous duties which the Astronomer Royal has felt it desirable to undertake in the public interest.
Under these circumstances it becomes a matter for serious consideration whether, unless adequate provision be made for the primary objects of the Observatory, extraneous work, such as the supply of time-signals, may not have to be dropped. The service of hourly time-signals till NS considerable work on myself and the staff of the Observatory, and, as it is purely voluntary, it appears to me that a condition of its maintenance must be that arrangements shall be made to enable the proper work of the Observatory to be carried on and suitably developed.
The Report here presented refers to the year from 1888 May 11 to 1889 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
The principal moveable instruments are thus distributed: -
At Greenwich - [the clocks at Greenwich were omitted from the list] …
On loan - Clocks.- "Dent No. 1916," and "Dent No. 2013," at the Cape Observatory, and "Dent No. 2011" at Kew Observatory. …
Owing to want of space in the Observatory buildings the moveable instruments, clocks, and other apparatus, which are not in actual use, are for the most part stowed away in their boxes in wooden sheds, where their periodical examination and renovation are attended with great difficulty. For the proper care of these instruments. it would be advisable that they should be housed in a brick building to serve as an Observatory museum for instruments and apparatus of scientific value or historical interest. A building of one storey, about 40 feet long and 30 feet broad, would be suitable for this purpose, and a convenient site could be found in the . South Ground, the proposed building being connected with the circular Lassell building. In that situation it would not interfere with the use of any of the astronomical or magnetical instruments, a consideration of much importance.
II.-Astronomical Observations:-
Transit-Circle.- ... Owing to pressure of work on the Greenwich-Paris longitude operations and other matters, the Personal Equation Instrument has not been used in the past year.
Clocks and Chronographs.- These are all in good order, except the Mean Solar clock, which requires cleaning after the disturbance caused by the renewal of the telegraph wires and batteries. The clock "Hardy," which had not been going well, was cleaned and repaired by Messrs. E. Dent & Co. in January.
VII. Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers and deck watches now being tested at the Observatory is 208 (159 box chronometers, 20 pocket chronometers, and 29 deck watches), 3 of which belong to the Indian Government, and the remainder to the Navy. The annual competitive trial of chronometers commences on July 6, and the trial of deck watches on October 26.
In the year ending 1889 May 10 the average daily number of chronometers and deck watches being regularly rated was 212, the total number received was 668, the total number issued was 601, and the number sent for repair was 282.
The following comparison shows the increase in these numbers since 1851:-
| 1851-1855. | 1881-1885. | 1888. | ||
| Average number being rated | 97 | 190 | 221 | |
| Average number received yearly |
291 | 475 | 654 | |
| Average number issued yearly |
270 | 494 | 599 | |
| Average number sent for repair yearly |
127 | 267 | 288 |
It will be seen that the work on chronometers has doubled in thirty years, and that there has been a further and more marked increase in the last five years, causing great pressure on the Observatory staff.
The annual trial of chronometers was more severe than in former years, as the chronometers have been tested in the oven at temperatures of 80° and 85°, as well as at temperatures of 95° and 97° Fahrenheit, so that any residual secondary error of compensation would be made evident in the range of temperature from 42° to 98°. Notwithstanding this, the performance of the chronometers generally has been very good, the first 23 (out of 47 sent in for trial) coming up to the standard for Naval service, The first six chronometers, as judged by their trial numbers, performed on the average better than the corresponding chronometers in any previous year, except 1886, when the conditions of the trial were not so severe.
For the annual trial of deck watches, 1888 Nov. 24 to 1889 Feb. 6, 32 watches were entered, and of these 17 were purchased for the Navy, the first 8 being classed "A," or equal in performance (on the 12 weeks' trial) to an average box chronometer. In future the duration of the trial will be increased to 16 weeks, viz., 6 weeks in the ordinary temperature of the room, 4 weeks in the oven, temperature 80° to 85° (the watches being tried in positions during the two middle weeks) and finally 6 weeks in the room.
Two chronometers have been tested for the Austrian Government, and four pocket chronometers for the Government of British Guiana.
There has been no failure in the automatic drop of the Greenwich time-ball, but on one day the ball was not raised on account of the violence of the wind.
The automatic drop of the Deal time-ball failed on thirteen days owing to interruption of the telegraph connections, and on one day high wind prevented the raising of the ball. There has been no case of failure of the 1 p.m. signal to the Post Office Telegraphs.
No return signals have been received from the Devonport time-ball clock since April 23, when, as I understand, the clock was cleaned and the contact-springs accidentally put out of adjustment. Up to that date the daily signal had been received regularly since the date of last Report, except on 42 days, of which 14 were Sundays. The apparent error of the clock-signal (after daily correction of the clock by the help of a time-signal from Greenwich) was under 0.2s on 66 per cent. of the days of observation, under 0.5s on 92 per cent., between 0.5s and 1.0s on 7 per cent., and it exceeded 1s on 1 per cent.
No further action has been taken as regards the proposal to establish hourly time-signals at the Lizard, as with the present pressure on the staff there would be great difficulty in making the necessary arrangements for securing the efficiency of such a time-service.
In the year ending 1889 May 10, there have been failures on 33 days in the automatic signals from the Westminster clock. The error of the clock was insensible on 33 per cent. of the days of observation, 1s on 28 per cent., 2s on 28 per cent., 3s on 8 per cent., and 4s on 3 per cent.
The transfer to the Post Office Telegraphic Department of the maintenance of the Observatory telegraph wires, batteries, and connections for communicating time-signals, which was proposed in June 1887, has been carried out, and the renewal of wires and apparatus is now practically complete. The work was commenced early in January and has occupied much more time than was originally anticipated. The Post Office authorities will now take charge of the wires and batteries up to test boards fitted near the various instruments and clocks, these latter remaining of course in our care. The new test boards fitted up by the Post Office will be of great use in localizing faults in the telegraphic circuits.
The re-determination of the difference of longitude between Greenwich and Paris was carried out last autumn, the Submarine Telegraph Company having courteously placed a spare wire at our disposal each night from 8 to 12, and the Post Office having provided the services of a clerk, and the use of a wire to London, where it was joined on to the Submarine wire, so as to give direct communication with Paris. Observations were made in four groups of three nights each (or the equivalent in half nights). An English and a French observer were stationed at each end, each with a separate instrument and chronograph, and the pairs of' observers were interchanged twice, to eliminate any change in the personal equations during the progress of the work. The pairs of English and French instruments were similar, and the signals as well as the star transits were recorded on similar chronographs. On a full night each observer recorded about forty star transits, reversing his instrument three times, and exchanged signals twice (near the beginning and end of the evening) with his compatriot at the other end of the line, and once with the other observer. At Greenwich the transits were referred to the Sidereal Standard clock, and comparisons with the large Greenwich chronograph enable the ordinary determinations of clock-error with the transit-circle to be utilized as well as those specially made with the portable transits. With this object transits of clock stars with the transit-circle were usually taken by four observers on each night during the longitude operations. The actual stations were the Front Court of the Royal Observatory and the Observatory of the Service Géographique de l'Armée at Paris, the position of which with reference to the Paris Observatory has been accurately determined. Commandants Bassot and Defforges were the French observers, and Mr. Turner and Mr. Lewis the English. The observations lasted from September 23 to November 15, and 18 nights of observation at both stations are available, the two English observers having observed at Greenwich 653 transits of clock stars and 165 of azimuth stars, and at Paris 778 transits of clock stars and 165 of azimuth stars. All of these, as well as the signals exchanged, have been read out from the chronograph registers and the reductions are far advanced. Subsidiary investigations of the value of a revolution of micrometer screw, of intervals of wires, of form of pivots, and of errors of the axis-level have consumed much time, the last-named having been a long and tedious discussion.
In connection with the re-determination of the Greenwich-Paris longitude, provision has been made for the determination of the difference of longitude between Greenwich and Dunkerque, and it has been arranged that the operations shall begin early in June. The observations will be made by one French observer (Commandant Defforges) and one English (Mr. Turner), and it is intended to obtain eight complete nights of observation at both stations, the observers being twice interchanged. Commandant Defforges also proposes to determine the difference of latitude between Greenwich and Dunkerque.
While stationed at Greenwich last autumn, Commandant Defforges took the opportunity of swinging his reversible pendulums, which were firmly mounted in the Safe Room, to determine the absolute force of gravity at Greenwich in connection with the French series of determinations.
The Indian invariable pendulum has recently been mounted under General Walker's supervision in the Record Room at Greenwich for observations similar to those made in India, in the United States, and at Kew. It is intended to commence the swings without delay, all arrangements being now complete, and a detailed programme of observation having been drawn up by General ·Walker. By these two operations the French and Indian pendulum determinations will be connected through Greenwich.
IX. General Remarks:-
The re-determination of the longitude of Paris was another duty which it was incumbent on us to undertake, and in connection with this the longitude of Dunkerque has to be determined this year. Both of these are laborious operations when superadded to the current work of the Observatory.
It may here be mentioned that the Observatory has been relieved of the charge of examining optical instruments for the Navy, which, in its recent developments, consumed much of my own time, and threatened to interfere seriously with our proper functions. But against this is to be set the increase of work in connection with chronometers and the close supervision necessary to secure the higher standard of efficiency now required in deck watches as well as in chronometers.
The Report here presented refers to the year from 1889 May 11 to 1890 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
The Ball-Lobby and the staircase leading to the Octagon Room have been painted; and also the room assigned as a private room to the Computers.
The principal moveable instruments are thus distributed: -
At Greenwich - [the clocks at Greenwich were omitted from the list] …
On loan - Clocks.- "Dent No. 1916," and "Dent No. 2013," at the Cape Observatory, and "Dent No. 2011" at Kew Observatory. …
II.-Astronomical Observations:-
Clocks and Chronographs.- The Sidereal Standard was cleaned in October, and the clock "Hardy" in January. The Mean Solar clock was cleaned in 1889 May, after the disturbance caused by the renewal of the telegraph wires and batteries on their transfer to the Post Office authorities. The clocks are at present all in good order.
VII. - Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers and deck watches now being tested at the Observatory is 165 (121 box chronometers, 19 pocket chronometers, and 25 deck watches). The annual competitive trial of chronometers commences on July 5, and the trial of deck watches on October 25.
In the year ending 1890 May 10 the average daily number of chronometers and deck watches being regularly rated was 209, the total number received was 663, the total number issued was 703, and the number sent for repair was 368.
The annual trial of chronometers (which Iasts for 29 weeks) has been rather more searching than that of last year, as the range of temperature to which the instruments have been subjected has been nearly continuous from 42° to 99°. The mean temperature of the room ranged from 50° to 67°, and in the oven the chronometers were tested at mean temperatures of 75°, 85°, and 90° to 96½°. Notwithstanding this increase of severity, the chronometers were found to compare well with those tested in former years, and the performance of the first on the list (as inferred from the trial number) has never been surpassed, and only once equalled (in 1882). The average "trial number" of the first six chronometers was 18.9, which compares favourably with the corresponding value in former years.
For the annual trial of deck watches, 1889 October 26 to 1890 February 15, 25 watches were entered, and of these 19 were purchased for the Navy, the first 13 being classed "A," or equal in performance (on the 16 weeks' trial) to an average box chronometer. The trial was four weeks longer than that of other years, and yet the performance is, on the average, better than in any previous trial, the performance of the first four watches being superior to that of the best watch hitherto tested.
Two chronometers have been tested for the Crown Agents for the Colonies; 7 for the Indian Government; and 2 for Dr. Gill.
Experiments have been made in the past year on the uniformity of rate in deck watches and chronometers with reference to the time elapsed since winding. In 1889 October two deck watches, one keyless, with going barrel, and the other an ordinary key-winder, with fuzee, were carefully compared several times during the day, but no systematic variation of rate could be detected. In 1890 February, 7 watches (all keyless) were compared at 0h, 2h, 4h, 6h, &c. after winding; but again no change of rate could be detected.
A somewhat different experiment was made with the box chronometers in the annual trial. These were wound for the last fortnight of the trial on alternate days, and the rates for the days on which they were wound were compared with those of the intermediate days. No systematic effect on the rate could be detected, except perhaps in the case of one chronometer near the bottom of the list in order of merit.
On 1890 January 25, the Greenwich time-ball was not raised on account of the violence of the wind; and on 1890 April 1 the springs of the Mean Solar clock failed to act, so that the ball did not drop, nor was any signal transmitted to the Post Office. There was also a failure in the 1 p.m. signal to the Post Office on November 27, but the fault was not at the Observatory. Owing to a mistake in the numeration of seconds on the chronograph, coupled with a sudden change of rate of the sidereal standard clock, the 1 p.m. signal was erroneous on September 2, 3, and 4. On all other days it was sent out correctly.
The automatic drop of the Deal time-ball failed on 21 days owing to interruption of the telegraph connexions, and on one day high wind prevented the raising of the ball. There have been frequent failures in the return signal, the arrangements for which are not in a satisfactory state. It appears that some time ago the Post Office authorities arranged for the substitution of a hand signal for the automatic return signal, which was found not to give a sufficiently long contact. The value of the return signal has thus been greatly diminished, and I propose to revert to the automatic signal, modified as regard the duration of contact, so as to suit the arrangements of the Post Office Telegraphs. It would be desirable that this signal should be sent at as short an interval as practicable after the ball-drop so as to serve as a check on the accuracy of the time-signal.
The contact springs of the Devonport time- ball clock having been readjusted after the failure mentioned in the last Report, signals have been received regularly since 1889 May 23, except on 26 days, of which seven were Sundays. The apparent error of the clock-signal (after daily correction of the clock by the help of a time-signal from Greenwich) was under 0.2s on 63 per cent. of the 337 days of observation, under 0·5s on 94 per cent., between 0.5s and 1.0a on 5 per cent.; and exceeded 1s on 3 days, all of them Sundays. Six of the 17 days on which the error exceeded 0·5s were also Sundays.
The automatic signals from the Westminster clock have not been received very regularly, there having been failures on 44 days in the year ending 1890 May 10. The error of the clock was insensible on 39 per cent. of the days of observation; it amounted to 1s on 42 per cent., to 2s on 18 per cent., and to 3s on 1 per cent.
Observations for the determination of the longitude, Dunkerque-Greenwich, were successfully carried out in June and July, a spare wire and the services of a clerk having been courteously placed at our disposal by the Post Office authorities. Two observers, Commandant Defforges and Mr. Turner, made observations in four groups of 2 nights each, or the equivalent in half nights, interchanging between the first and second group and again between the third and fourth. The reductions are complete as far as the first approximation to the result, but the final reduction of this longitude and also of the Paris-Greenwich longitude, for which observations were made in 1888, has been delayed by the discussion of a curious discrepancy between the results obtained for clock error at one of the stations in the latter by the two instruments mounted side by side, and used by the French observer and the English observer respectively. The difference amounts to nearly 0.5s, [a misprint for 0.3s] but it has not yet been found possible to say with certainty which of the instruments has given an erroneous result. The two instruments used by the Greenwich observers were set up side by side in the Front Court on 1890 April 17, and a number of observations made with them simultaneously "by Messrs. Turner and Lewis, showed a perfectly satisfactory accordance. Commandant Defforges proposes to come to Greenwich very shortly to discuss the results in reference to this discrepancy in concert with the Greenwich observers.
By request of the French observers, the difference of latitude between Greenwich and Paris was determined in July by simultaneous observations, with similar instruments. The result inferred for Greenwich is within 0.1s of the adopted value.
During last summer, Lieutenants A. M. Field and H. E. Purey Cust, R.N., made a series of observations on the relative advantages of the portable transit and sextant, for determining local time, their report to the Admiralty being in favour of the former.
It was mentioned in the last Report that the Indian invariable pendulums had been mounted in the Record Room under General Walker's supervision. The three pendulums have each been swung 8 times, at pressures of both 2 inches and 27 inches, and the observations completely reduced, giving the following results for number of vibrations in a mean solar day, reduced to vacuum, a temperature of 62°, an infinitely small arc, and sea-level; the corresponding values obtained at Kew being appended for comparison:-
| Pendulum. | Greenwich. | Kew. | |
| 4 | 86,165.54 | 86,166.50 | |
| 6 | 86,065.70 | 86,066.61 | |
| 11 | 86,117.04 | 86,117.03 |
A clock with a new form of compensation was tested for Mr. R. Inwards for several months during the past autumn and winter.
IX. General Remarks:-
Several proposals have been made to me recently for the telegraphic determination of the difference of longitude between Greenwich and stations which are important in connection with Geodetic Surveys. The Superintendent of the McGill College Observatory, Montreal, has asked for the co-operation of Greenwich in a direct determination of longitude, with a view to making that Observatory the base station for the Geodetic Survey of Canada, the Canadian Pacific Telegraph Company having offered the use of their lines and connecting cable for the purpose. A re-determination of the longitude of Washington is proposed by the Superintendent of the United States Coast Survey, and in connection with this it may be advisable to fix the longitude of Porthcurno (the terminus of the trans-Atlantic cables). Lastly, M. Otto Struve has urged the importance of re-determining with improved modern appliances the longitude of Valentia, as the extremity of the great European arc of longitude. It seems desirable that the Royal Observatory should take part in these operations, and the experience gained in the observations for the longitude of Paris and Dunkerque would greatly facilitate the work. Some additions to our instrumental appliances would be necessary for these and other longitude determinations which it might be expedient for us to undertake in the future.
The Report here presented refers to the year from 1890 May 11 to 1891 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
In consequence of a recent decision of the Admiralty to largely increase the number of chronometers and deck watches for the Navy, additional accommodation for chronometers is required immediately, the space in the present Chronometer Room being insufficient even for existing requirements. A proposal is now under the consideration of the Admiralty to provide this by appropriating the room under the Chronometer Room and the Lower Record Room to chronometers, the South wing of the proposed Physical Observatory being built to receive the contents of these two rooms,
The principal moveable instruments are thus distributed: -
At Greenwich - [the clocks at Greenwich were omitted from the list] …
On loan - Clocks.- "Dent No. 1916," and "Dent No. 2013," at the Cape Observatory, and "Dent No. 2011" at Kew Observatory. …
II.-Astronomical Observations:-
Clocks and Chronographs.- The Sidereal Standard was cleaned in April and the clock "Hardy" in December. The clock" Dent 2017" was mounted in the dome for sidereal photography on 1891 March 14; and" Dent 2016" is now being fitted with contact springs for use in longitude operations. The clocks are at present all in good order.
A pin in the chronograph gave way on 1890 June 9 causing some damage, which was however promptly repaired, and the instrument has since been in good order. Two portable chronographs are being made by Mr. Hilger for use in longitude work and are nearly complete
VII. - Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers and deck watches now being tested at the Observatory is 169 (113 box chronometers, 20 pocket chronometers, and 36 deck watches). The annual competitive trial of chronometers commences on July 4, and the trial of deck watches on October 24.
In the year ending 1890 May 10 the average daily number of chronometers and deck watches being regularly rated was 200, the total number received was 617, the total number issued was 628, and the number sent for repair was 269.
The annual trial of chronometers (which lasts for 29 weeks) was still more searching than that of the previous year, the range of' temperature to which the instruments were subjected having been nearly continuous from 34° to 100°. The weekly mean temperature of' the room ranged from 43° to 67°, and in the oven the chronometers were tested at mean temperatures of 75°, 85°, and 92° to 98°. The "trial numbers" however, compare well with those of former years, and the first chronometer is a very fine one. The average trial number of the first six chronometers was 20.3.
For the annual trial of deck watches, 1890 October 25 to 1891 February 14, 31 watches were entered, and of these 22 were purchased for the Navy, the first 5 being classed "A," or equal in performance (on the 16 weeks' trial) to an average box chronometer. Owing to the exceptionally cold weather of the past winter, the trial has been more severe than usual, and the performance of the watches is not, on the whole, so good as in the previous year. The first watch has, however, a slightly smaller trial number than the first of last year, In future trials the watches will be separated into two classes, A and B; and for those entered as of Class B, the trial in positions will be limited to "dial up" and "pendant up," these watches being intended for ordinary use on board ship, whilst the watches of Class A would serve as pocket chronometers.
Nine chronometers have been tested for the Austrian Government.
Harrison's two machines for measuring time, his prize chronometer, and Larcum Kendall's copy, with nine chronometers exemplifying various stages of development, one pocket chronometer, one deck watch, and the working model of' a chronometer, have been lent to the Naval Exhibition at Chelsea.
The want of space in the chronometer room has been felt in various ways. Owing to the crowded state of the shelves it has not been found practicable to place trial chronometers in different positions with reference to the magnetic meridian, in order to ascertain whether their rates are influenced by terrestrial magnetism, and the testing of navy chronometers and deck watches has been carried out with much difficulty at times. In view of the large proposed increase in the number of chronometers to be purchased annually, and the consequent probable increase in the number entered for trial, the allotment of more space to chronometers has become imperative, and I propose to use in this connexion the room immediately below the present chronometer room as soon as space can be provided in the new buildings for the mechanician, who now works there, for the instruments, &c., at present stored there, and for the convenient transaction of other business (such as the reception of chronometer makers, the packing of publications, &c) to which this room is occasionally devoted. In the meanwhile, a little space may be gained in the chronometer room by fitting up shelves for deck watches round the central pillar.
On 1890 November 7, the Greenwich time-ball was not raised on account of the violence of the wind; and on'1891 March 1 the springs of the Mean Solar clock failed to act, so that the ball did not drop, nor was any signal transmitted to the Post Office. On 1890 December 27, the train of the Mean Solar clock dropped 2sec. and the signal was in error to this amount. On all other days it was sent out correctly.
The automatic drop of the Deal time-ball failed on 17 days owing to interruption of the telegraph connexions, and on one day high wind prevented the raising of the ball. As mentioned in the last Report, arrangements have been made for reverting to the automatic return signal from Deal, modified so that it is made at an interval of eight seconds only after the ball drops, to serve as a check on the accuracy of the time-signal. This arrangement was finally brought into action on 1890 December 18, and with a few exceptions has performed extremely well. The beginning and end of the signal are both observed, and it is found that the beginning is more regular than the end, the average error in the former, as observed, being only about 0·1s. The duration of the signal has gradually lengthened from about 2s in December to 3·7s in May, which would seem to point to some wear in the contacts.
Signals from the Devonport clock have been received regularly since the date of the last Report, except on 30 days when the signal totally failed, or was interrupted by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by the help of a time-signal from Greenwich) was under 0.2s on 69 per cent. of the 333 days of observation, under 0.5s on 95 per cent., between 0.5s and 1.0s on 5 per cent., and exceeded 1s on one occasion only, and that a Sunday. Nine of the 14 days on which the error exceeded 0.5s were also Sundays.
The automatic signals from the Westminster clock have been received regularly throughout the year ending 1891 May 10, except on 14 days when the signal failed. The error of the clock was insensible on 42 per cent. of the days of observation; it amounted to 1son 29 per cent., to 2s on 22 per cent., to 3s on 5 per cent., and to 4s on 2 per cent.
To reduce the tendency to give sparks at the contact springs, condensers have been placed by the Post Office authorities in all the clock and observing circuits which require them, and the arrangement has worked quite satisfactorily.
The reductions for the longitude Paris-Greenwich are now completed and ready for publication. In reference to the discrepancy between the results of the French and English observers, mentioned in the last Report, Commandant Defforges visited Greenwich in 1890 June, and went carefully through the reductions with Mr. Turner and Mr. Lewis. No mistake was found in the work but several questions of some importance were raised. The results of the discussion and of subsequent correspondence are summed up in two papers by Mr. Turner and one by Colonel Bassot and Commandant Defforges, in the Monthly Notices of the Royal Astronomical Society, Vol. LI., pp. 155, 407, and 413 respectively. As the matter now stands the English definitive result for the difference of longitude between the Greenwich Transit Circle and Cassini's Meridian is 9m 20.86s, while the French result (not yet published) is about O.15s greater, a discordance which though only about half of that found in the preliminary discussion, is still so large, that there seems to be no alternative but to repeat the work with special precautions suggested by the experience gained.
The reductions of the longitude Dunkerque-Greenwich have been delayed by the above discussion, but are now proceeding.
The proposal to determine the longitude of Montreal as the base station for the Geodetic Survey having been sanctioned by the Admiralty last December, arrangements have been made in concert with Prof. McLeod of the McGill College Observatory, Montreal, for a determination of the longitudes Montreal-Canso- Waterville-Greenwich, the termini of the cable, Canso and Waterville, being occupied as longitude, and not merely as transmitting stations, a course which seems advisable in view of the great geodetic importance of these points. The necessary funds have been voted, and the Commercial Cable Company have generously placed their cable at our disposal. It is proposed to use the portable transits B, C, D & E for this work, four observers being engaged, each of whom shall carry with him from station to station his own instruments. The chronographs for the two English observers are being constructed by Mr. Hilger, and the electrical apparatus is being supplied by Messrs. Siemens. After a preliminary visit of Prof. McLeod to Canso, and of Mr. Turner to Waterville, to settle the observing sites and other general arrangements, it is hoped that one stage of the operations may be completed in August and September of this year, but without any observer crossing the Atlantic, for which, owing to delays beyond our control, we shall scarcely be prepared in the present year. The interchange of observers will be effected next year at a time to be hereafter determined, precautions being of course taken to check any change in personal equation.
The determination of the longitude of Washington has been deferred for the present.
During the past year, Lieutenants Heming, Monro, and Smyth, R.N., and Captain Haynes, R.E., have at various times been instructed in transit observing. Mr. S. Hirayama, of the Tokio Observatory, was at work for some weeks studying the general organization of the Observatory.
IX. General Remarks: -
The preparatory work for the photographic map of the heavens has occupied a good deal of attention during the past year …
The same difficulty has been felt in reference to the important work of determination of longitudes, in which the Royal Observatory should naturally take part. The discussion of the results for the longitude Paris-Greenwich in 1888 has brought to light various difficulties which seem to attend all such operations and to lead to uncertainty in the result. The removal of these difficulties has been a subject or anxious consideration as a preliminary to the determination of the longitude of Montreal and the redetermination of the longitude of Paris, but, under the circumstances of the past year, it has been found extremely difficult to give the requisite amount of thought to the working out of the conditions essential to success.
Recently attention has been called to the crowded state of the chronometer-room, which makes it impracticable to receive the additional number of chronometers now required for the Navy until more space has been provided.
The Report here presented refers to the year from 1891 May 11 to 1892 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
The Admiralty have authorized the building of the South wing of the proposed Physical Observatory during the present financial year, in order to provide additional accommodation for chronometers and deck watches, the room under the Chronometer Room and the Lower Record Room to be appropriated to chronometers as soon as the South wing is ready to receive the contents of these two rooms.
The principal moveable instruments are thus distributed:-
At Greenwich- [the clocks at Greenwich were omitted from the list] …
At Waterville (temporarily for Montreal longitude)-
Transit E, clock Dent 2016, a portable chronograph, a relay, u galvanometer, and a rheostat.
On loan-
Clocks.- Dent, No. 1916, and Dent, No. 2013, at the Cape Observatory, and Dent, No. 2011, at Kew Observatory.
For use in longitude operations, two portable chronographs by Hilger, and two relays, two galvanometers, and two rheostats by Siemens, have been obtained.
Owing to the pressure of the Montreal longitude work, the annual comparison of the books and manuscripts with the Catalogue has not yet been completed.
II.-Astronomical Observations:-
Clocks and Chronographs.- The daily rate of the Sidereal Standard clock changed rather suddenly from 1.0s to 2.0s gaining in October last. On enquiry it was found that workmen had been fixing a new shelf in the magnet-basement near the clock, and the necessary hammering in the neighbourhood had doubtless caused this change. Since then the rate has been steady, although it was deemed expedient to reduce this large rate by mechanical adjustment.
The clock "Dent 2016" was fitted with contact springs and sent to Waterville in April, in connexion with longitude operations. It was placed in the Artificial Cable Room at the Telegraph Station, where the temperature is kept approximately uniform, and under these conditions its rate was found to be remarkably steady. The clock “Graham 2" was mounted in the Transit Pavilion in August last, but has been dismounted for transport to Paris, in connexion with the redetermination of the longitude, Paris-Greenwich. These and other clocks are at present all in good order.
The two portable chronographs made by Mr. Hilger have performed satisfactorily, after some trouble spent in adjustment.
VII. - Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers and deck watches now being tested at the Observatory is 157 (91 box chronometers, 19 pocket chronometers, and 47 deck watches). The annual competitive trial of chronometers commences on July 2, and the trial of deck watches on October 22.
In the year ending 1891 May 10 the average daily number of chronometers and deck watches being regularly rated was 243; the total number received was 765, the total number issued was 750, and the number sent for repair was 442.
For the annual trial of chronometers (which lasted for 29 weeks) with a range of temperature from 41° to 100°, 51 chronometers were sent in, and of these 22 have been purchased for the Navy. The performance of the chronometers generally was good, and the average trial number of the first six was 21.4, which compares well with: those for previous years.
For the annual trial of deck watches, the watches were separated into two classes, A and B, 72 being entered (by their makers) as A and 21 as B, the trial in positions for the latter (which are intended for ordinary use on board ship) being limited to ''dial up" and "pendant up." Of these, 65 have been purchased for the Navy, 22 being classed as A, and 43 as B, on the results of the trial, 22 of the latter having been entered for Class A by their makers. The first two watches in Class A were exceptionally good.
Harrison's machines for measuring time and the chronometers lent to the Royal Naval Exhibition have been returned.
New shelves have been fitted up in the Chronometer Room round the central pillar for deck watches, but notwithstanding this there was not sufficient shelf-room during the trials of chronometer and deck-watches, with the result that they could not be kept in orderly arrangement – a serious difficulty in providing for their safe custody,
On 1891 October 14, December 10 and 13, the Greenwich time-ball was not raised on account of the violence of the wind; and on 1892 April 1 the springs of the Mean Solar clock failed to act, so that the ball did not drop, nor was any signal transmitted to the Post Office. On October 19, through sudden failure in the electric train of the Mean Solar clock, the signal at 13h was 8s late. On November 22 (Sunday) the Greenwich signal did not reach the General Post Office through failure in the connections outside the Observatory. On all other days the time-ball was dropped correctly.
The automatic drop of the Deal time-ball failed on 12 days owing to interruption of the telegraph connexions, on one day (November 11) high wind prevented the raising of the ball, and on February 18, the ball was not raised as some alterations were being made in the cylinder. On October 19, the ball was dropped 8s late through the error in the Greenwich signal previously mentioned. On this occasion it was raised again and dropped by hand at 14h.
There were repeated failures III the automatic return signal from Deal last November, and it was ultimately found by Captain Wrottesley, R.E., of the Post Office Telegraphs (who gave much personal attention to the matter), that these were due to the accumulation of grease which for many years had been applied to the piston on account of the excessive windage in the cylinder, intended to act as an air cushion. Under the supervision of Captain Wrottesley, to whom my thanks are due for his valuable assistance, the cylinder was taken to pieces and cleaned out on February 17, (after the ball drop at 13h) and the windage having been corrected by an asbestos pad, it was remounted. on February 18, the ball being dropped by hand at 14h on that day. The signal has since been received regularly, though the times of beginning and end vary from time to time by one or two seconds.
Signals from the Devonport clock have been received regularly since the date of the last Report, except on 51 days when the signal totally failed, or was interrupted by telegraph signals. The apparent error of the clock signal (after daily correction of the dock by the help of a time-signal from Greenwich) was under 0.2s on 61 per cent. of the 312 days of observation, under 0.5s on 91 per cent., between 0.5s and 1.0s on 11 per cent., and exceeded 1s on two occasions only.
The automatic signals from the Westminster clock have been received regularly throughout the year ending 1892 May 10, except on 14 days when the signal failed. The error of the clock was insensible on 58 per cent. of the days of observation; it amounted to 1s on 30 per cent., to 2s on 7 per cent., to 3s on 4 per cent., and to 4s on 1 per cent.
The publication of the observations for the Paris-Greenwich longitude in l888, and of those for the Dunkerque-Greenwich longitude in 1889, has been delayed pending a redetermination of the former longitude which will be commenced on June 6 of the present year; and it is hoped to settle several questions of importance raised by the discussion of the results obtained in 1888.
The first stage of the operations for the longitudes Montreal-Canso- Waterville-Greenwich was completed on Sunday night, May 23. In May of last year Mr. Turner paid a preliminary visit to Waterville, the terminus of the cable kindly placed at our disposal by the Commercial Cable Company. He selected a site for the transit after consultation with Major Johnston, of the Ordnance Survey; and discussed the general arrangements with the Telegraph Superintendent, Mr. T. J. Wilmot, and several experiments were made on the best method of transmission of signals. It was found that these could be sent and received either directly with the siphon-recorder, the clock taps and sent signals being recorded by slightly upsetting the balance of the bridge used in the duplex method; and the signals from Canso being received in the ordinary way; or that a chronograph might be used, the siphon-recorder being converted into a very delicate relay by attaching to the suspension-thread, a very light aluminium rocker, which would dip into mercury on being disturbed and so complete a circuit. This last device was suggested by the Superintendents at Waterville and Canso, and found to work satisfactorily. It was especially useful in transmitting signals direct from Montreal to Greenwich and back, which was, done on Sunday 1892 May 23. In May 1891 however the exchanges were only experimental, though it was found in the course of
them. that the time of transmission along the Cable Waterville-Canso was about a quarter of a second, – a result confirmed by a rough comparison of signals on 1892 May 11. Professor McLeod of Montreal paid a similar preliminary visit to Canso in 1891 June, and found an accordant value for the time of transmission.
Portable Transits B, C, D, and E were to be used for the time-determinations at the four stations, one instrument to ,be appropriated to each observer and considered as forming part of him. Several improvements in details were found necessary, especially in the mounting of the object glasses, which experience in 1888 had shewn to be unsatisfactory. New striding levels were also made, mounted on aluminium forks, and a micrometer screw attached to each (according to a suggestion made by Mr. Turner), so as to avoid the use of the defective bubble scales. The transits B and, C were sent to Montreal in August, after testing them as well as was practicable under the tent-covering of the Transit Pavilion, whose semi-domes. had not yet arrived. Two chronographs with stylographic pens had been made by Mr. Hilger, and four tables of electrical apparatus were constructed on the general principle of the French chronographs used in 1888 and 1889, but in a more compact form. The relays, rheostats and galvanometers were supplied by Messrs. Siemens Brothers, who kindly gave us considerable assistance in this matter. Two of these tables were sent to Montreal and used in the operations at Montreal and Canso, but a different plan of operations was ultimately adopted at Greenwich and Waterville. A transit hut was sent to Waterville in August, and erected under Mr. Wilmot's supervision. These preparations and unexpected small delays had taken so much time that it was found impossible to complete the work in 1891 before the winter, and the date of commencement was altered by agreement to 1892 April 19. Mr. Turner went to Waterville on April 11, taking with him his instruments and the clock Dent 2016. This Clock was mounted in the Artificial Cable Room at the station, where the temperature is kept nearly uniform, and has under these conditions performed extremely well. Signals were exchanged between Greenwich and Waterville twice each night from April 18-26, and again from May 5-12, when Mr. Hollis was at Waterville and Mr. Turner at Greenwich, and between Canso and Waterville once or twice each night during the same periods; and, also on May 13, 14, 15 (after the date of this Report), when there was interruption between Greenwich and Waterville, the siphon-recorder being, used according: to the first method above described. Through signals between Greenwich ana Montreal were exchanged on Sunday May 23, using the siphon-recorders as relays for connexion at Waterville and Canso, It was found by experiments in 1891 that the virtual time of action of these relays was about 0.2s, the rocker not responding until the received current reached a certain strength.
Time determinations were made in all on 14 nights at Greenwich, 12 at Waterville, and about the same number at Canso and Montreal, our information not being quite complete on this head. A preliminary reduction give's every promise of satisfactory accuracy at Greenwich and Waterville.
Professor McLeod will reach here in July, bringing with him some account of his observations; and after discussion with him, Mr. Turner will leave for Montreal early in August.
In February and again in March, Captain Grant, R.E., of the Ordnance Survey Office, came to the Observatory to consult me as to the determination of the boundary of Mashonaland, in conjunction with the Portuguese Government, and to practise the requisite transit observations. The most difficult part of this operation was the fixing of a meridian of longitude on the spot, and without, of course, any possibility of telegraphic communication. I recommended the method of Moon culminations, observed with a small transit, which was specially made by Messrs. Troughton and Simms; and to minimize the errors of this method, a rough prediction of the Moon's errors was made. For this purpose all the observations of R.A. of the Moon made in the years 1883-1891 were collected, and arranged as though the lunations corresponded to calendar months; that is the errors on the day of full Moon in the first lunatation of each year were considered together and plotted in a curve, which was then produced conjecturally to get the error on the day of full Moon in the first lunation of 1892; and similarly for other lunations, and other epochs in the lunation, before or after full Moon. About one broad general feature of the curves there was no doubt, viz:- the error is larger algebraically after full Moon than before, and this excess is large in summer, and small in winter. A possible explanation would be, that the adopted diameter is too large, being deduced from observations made at the full when the sky is darkest, and irradiation increases the apparent diameter to the maximum extent. In summer there is diffused light from the sky even near midnight, and irradiation is not so large; consequently transits of the second limb give apparently a larger tabular error than those of the first.
During the past year the apparatus for the Singapore time-ball, about which the Crown Agents for. the Colonies had consulted me, was tested and ultimately made satisfactory, after some alterations suggested by me had been made. A chronograph for Hong .Kong Observatory, made by Sir H. Grubb has also been tested, and after some adjustment found to be very satisfactory;
IX. General Remarks:-
The longitude operations, which are occupying so much of our attention during the present year, are directed not only to the fixing of the longitudes of Montreal and Paris with all possible accuracy, but also to the determination of the longitude of Waterville (the terminus in Ireland of the Commercial Company's cable) as a geodetic station at the western extremity of the great European arc ·of longitude. The longitude of this station, however, as well as that of Valentia (determined many years ago), may, not improbably, be affected by considerable local attraction, situated, as they both are, between the Atlantic on the west, and a mountain mass on the east. It would, therefore, be very desirable in the interests of geodesy, that the longitude of a station on the other side of this mountain mass should also be determined, and I would suggest Killorglin, at the head of Dingle Bay, as probably the most suitable for the purpose.
The Report here presented refers to the year from 1892 May 11 to 1893 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
The building of the South wing of the proposed Physical Observatory, in order to provide additional accommodation for chronometers and deck watches, was commenced on November 24 last, but was interrupted on March 4, on arriving at the first floor, by a failure in the supply of terra cotta. Building operations are now about to be re-commenced.
An inventory of moveable property has been completed as far as circumstances would allow, a portion of the old instruments and apparatus being stored in sheds, where they are not at present accessible for examination. This inventory will require thorough revision when the completion of' the new Physical Observatory allows of a rearrangement on a more permanent basis, and, in the meanwhile, considerable changes in the storage of the moveable property will result from the utilization of the new glass cases in the Museum building.
The principal moveable instruments are thus distributed:
At Greenwich-
On loan-
Clocks. - Dent, No. 1916, and Dent, No. 2013, at the Cape Observatory; Dent, No. 2011, at the Kew Observatory; and Dent, No. 2010, at Devonport.
The instruments used in the longitude operations of last year have all. been safely 'returned from Montreal, Canso, and Waterville, with the exception of Transit C, which is still at Montreal for adetermination of personal equation between Prof. McLeod and Mr. Klotz.
II.-Astronomical Observations:-
Clocks and Chronographs. - The Sidereal Standard has required more attention than usual during the past year. On 1892 June 26 it was found stopped, though wound up sufficiently for another 2 days; on September 3, after going very erratically, it was examined and repaired by Messrs. E. Dent & Co., who reported that the oil had thickened on the escape pivots; the clock was again examined on 1893 February 13, suspicion having been entertained that it stopped during winding; the maintaining power was found defective and strengthened; and on 1893 May 4 it was noticed that the barometric inequality was (and apparently had been for some time) considerably under-corrected, and an alteration was made with a view to its more complete compensation.
The Mean Solar Clock was cleaned by Mr. Kullberg on 1892 May 27, the signals at 10h and 13h not being interfered with. The clock Hardy was repaired on May 30; and the clock Mudge and Dutton was cleaned on January 10.
With a view to the improvement of the hourly time signals the clock Dent 2012 with zinc and, steel pendulum had been fitted with hourly contact springs and mounted in the Ball Lobby to replace the electrical Mean Solar Clock, but it was not brought into use pending arrangements for working the sympathetic dials by reverse currents at the alternate seconds. Mr. Kullberg is now fitting seconds contact springs which will it is hoped effect this, and the new clock, which has a very steady rate, will be brought into use for the hourly time-signals as soon as possible.
VII.-Chronometers, Time Signals, and Longitude Operations:-
The number of chronometers and deck-watches now being tested at the Observatory is 206 (137 box chronometers, 26 pocket chronometers, and 43 deck-watches). In addition to these there are 8 chronometers on trial for purchase by the Indian Government; and 4 box chronometers and 2 pocket chronometers have been tested after repair for the same Government. The next annual competitive trial of chronometers commences on July 1, and the trial of deck-watches on October 21.
In the year ending 1893 May 10 the average daily number of chronometers and deck-watches being regularly rated was 274; the total number received was 759, the total number issued was 761, and the number sent for repair was 422.
For the annual trial of chronometers (which lasted for 29 weeks) with a range of temperature of from 37° to 103°, 48 chronometers were sent in, and of these, 25 have
been purchased for the Navy. Considering the exceptionally severe nature of the trial, owing to the low temperature in January, the chronometers purchased compare favourably with those holding corresponding positions in last year's trial; the average trial number of the first six being 20.0, as compared with 21.4 last year.
For the annual trial of deck watches, the watches were separated into two classes, A and B, 38 being entered (by their makers) as A and 10 as B, the trial in positions for the latter (which are intended for ordinary use on board ship) being limited to "dial up" and "pendant up." Of these, 43 have been purchased for the Navy, 35 being classed as A, and 8 as B. The performance of the watches in both classes, however, compares somewhat unfavourably with last year's, but the conditions were more severe owing to the low temperature in January. Many of the watches in Class A were not satisfactorily adjusted for temperature compensation, and were returned to the makers for adjustment before final purchase, necessitating a further trial of nine weeks (1893 August 26 to October 28) on their return to the Observatory.
On 1892 July 20, August 30, and 1893 February 10, the Greenwich time-ball was not raised on account of the violence of the wind; on 1892 December 25, and 1893 March 23, the ball failed to drop correctly at 13h and was raised again and dropped at 14h; and on 1892 May 31, the ball was accidentally dropped 1min. before 13h. On all other days it was dropped correctly. On 1892 June 26, July 10 (Sunday), and 1893 March 23, the Greenwich signal did not reach the General Post Office through failure in the electric connexions. The signal was considerably in error on the following dates through accidental circumstances:- 1892 September 21, 0·7s late; 1892 October 2, 1.3s late; 1892 December 12, 1.0s late; and 1892 December 18, 2.3s early.
The automatic drop of the Deal time-ball failed on 9 days owing to interruption of the telegraph connexions, and on three days when no signal left Greenwich; on one day, (February 10) the ball was not raised owing to high wind. Some difficulty having been experienced with the automatic return signal, the Post Office Authorities arranged to revert to the hand signal, which has been in use from September 6. The automatic return signal was reintroduced on May 9, after I had inspected the arrangements at Deal.
Signals from the Devonport clock have been received regularly since the date of the last Report, except on 55 days when the signal totally failed; or was interrupted by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by the help of a time-signal from Greenwich) was under 0·2s on 71 per cent. of the 304 days of observation, under 0·5s on 90 per cent., and exceeded 1s on one occasion only.
A similar clock corrected daily by help of a time-signal from Greenwich, automatically starting an auxiliary seconds pendulum, has been established at Portsmouth for dropping the time-ball, and return signals from it have been received here regularly at 13h 0m 20s since November 18 last, except on 28 days when the signal totally failed or was interrupted by telegraph signals. Information is sent to the Commander-in-Chief at Portsmouth whenever this signal is sensibly in error. The error was under 0.2s on 61 per cent. of the 140 days of observation: under 0.5s on 96 per cent., and between 0.5s and 1.0s on 4 per cent., never exceeding 1.0s.
The automatic signals from the Westminster clock have been received regularly throughout the year ending 1893 May 10, except on 25 days when the signal failed. The error of the clock was insensible on 42 per cent. of the days of observation; it amounted to 1S on 29 per cent., to 2s on 21 per cent., to 3s on 7 per cent., and to 4s on 1 per cent.
During the past year a Sidereal Clock and a Mean Time Clock made by Mr. Kullberg, and intended for use with the Singapore time-ball, and a clock by the same maker intended for the Natal Observatory, have been tested at this Observatory. The transit instrument made for Singapore by Messrs Troughton and Simms was also examined.
Longitude Operations: Immediately after Visitation Day last year, operations were commenced for the re-determination of the longitude of Paris. Four observers, two French and two English, took part in the work, as in 1888; three of them were the same as before (Colonel Bassot, Commandant Defforges, and Mr. Turner), but Mr. Hollis replaced Mr. Lewis, whose special attention was required in the Time department. The plan of operations adopted in 1888 was only modified in the following particulars: two clocks were used instead of one, at each end of the line, and all the clocks were placed in rooms kept at nearly constant temperature. The Sidereal Standard was used by the English observer at Greenwich throughout. The English observers used the small chronographs procured for the Montreal longitude, with one pen only, thus avoiding the troublesome correction for parallax of pens.
In the first part of the operations, Commandant Defforges and Mr. Turner were at Greenwich, Colonel Basset and Mr. Hollis at Paris. Signals were exchanged on 7 nights, on 4 of which clock error was determined at Greenwich and on 6 at Paris.
In the second and third parts the observers were interchanged; signals were exchanged on 11 nights, observations of stars for clock error being obtained on 8 of these, both at Greenwich and at Paris.
In the fourth part, the observers returned to their original stations. Signals were exchanged on 11 nights, clock errors being determined on 5 nights at Greenwich and on 9 nights at Paris.
The preliminary discussion of the English results for the difference of longitude between the Greenwich transit circle and Cassini's meridian is now complete, the mean of 25 practically independent determinations, after correcting for personal equation, being 9m 20.82s. The value found in 1888 by the English observers was 9m 20·85s.
In July Prof. McLeod came to Greenwich to discuss the first stage of the operations for the longitudes Montreal-Canso-Waterville-Greenwich. It appeared that the cable signals were for practical purposes as accurate as those over the land lines; and thus the chief difficulties of the work are, as in other cases, simply those of absolute time determination.
The second stage of the operations was commenced on August 16, and completed on September 16. It consisted of two parts, in the first of which the observers at Montreal, Canso, Waterville, and Greenwich were Mr. Turner, Mr. Klotz, Mr. Hollis, and Prof. McLeod respectively; signals being exchanged on every night (except in one or two cases of accidental interruption) from August 16 to August 30, and clock errors being obtained at the several stations on 8, 6, 6, and 11 nights respectively.
The observers were then interchanged to the following order:- Mr. Klotz, Mr. Turner, Prof. McLeod, Mr Hollis. Signals were exchanged each night from September 3 to September 16, and clock errors were obtained on 6, 12, 6, and 10 nights respectively.
The total number of nights on which there was complete connexion by signal between Greenwich and Montreal was 20.
The sidereal observations made by the Greenwich observers, and the signals, are completely reduced; but we have not yet received from Montreal the results of the time determinations by Prof. McLeod and Mr. Klotz.
In 1892 July, Commandant Defforges mounted his "relative" pendulum apparatus in the Record Room and made determinations of the force of gravity. He subsequently took the same apparatus to Leith Fort, Edinburgh, where Sabine had made observations; and during his work there time signals were sent him from this Observatory.
Early in April last, Col. Von Sterneck, of Vienna, mounted his pendulum apparatus on the same spot, and made a complete series of observations. He repeated the observations at the Kew Observatory.
IX. General Remarks:-
The work of the Observatory during the past year has been carried on under circumstances of exceptional difficulty. In the first place the operations for the determination of the longitudes of Paris and Montreal involved the absence of the Chief Assistant and of another Assistant for protracted periods during last summer and autumn. …
The Report here presented refers to the year from 1893 May 11 to 1894 May 10, and exhibits the state of the Observatory on the last-named day.
I. Buildings and Grounds, Moveable Property, and Library:-
The principal moveable instruments are thus distributed:-
At Greenwich-
On loan-
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the Oxford University Observatory,
II.-Astronomical Observations:-
Clocks and Chronographs. - The Standard Sidereal clock has been going very well during the past year, The alteration in the barometric correction mentioned in the last Report seems to have lessened the amount of error, The discussion of the rate has been deferred until a longer period of observation is secured.
The tappers of the chronograph which had been worn out were renewed in January. The clock Hardy was repaired on January 12, and Dent 2017, which is in the Astrographic dome and was found to be rusty, on March 3.
The adaptation of the mean solar clock Dent 2012, with zinc and steel pendulum, to send out the hourly signals and work the sympathetic dials by reverse currents at the alternate seconds, was completed by Mr. Kullberg on 1893 May 21, and from that date all signals were sent by this clock instead of by the electrical mean solar clock Shepherd. The clock worked satisfactorily till 1894 Jan. 20, when the contacts began to fail, and as it could not be relied on to drive the Observatory sympathetic dials satisfactorily, the clock Shepherd was generally used from that date till May 4, when a new set of contacts was applied to Dent 2012, and since then it has worked the sympathetic dials and sent out the hourly signals satisfactorily. Advantage was taken of the break to arrange for substituting the clock Dent 2012 for Shepherd, or vice versâ without loss of time.
VII - Chronometers, Time Signals, and Longitude Operations: -
The number of chronometers and deck-watches now being tested at the Observatory is 268 (159 box chronometers, 18 pocket chronometers, and 91 deck-watches). In addition to these, there are on trial for purchase by the Indian Government 5 two-day chronometers for the Mathematical Instrument Office, Calcutta, and 1 eight-day for Colaba Observatory. In the year ending 1894 May 10, the average daily number of chronometers and deck-watches being regularly rated was 320; the total number received was 947, the total number issued was 882, and the number sent for repair was 471. During the year 26 box chronometers, 3 pocket chronometers, and one deck-watch have been tested for the Indian Government.
For the annual trial of chronometers (which lasted for 29 weeks) with a range of temperature from 35° to 104°, 43 chronometers were sent in, and of these, 23 have been purchased for the Navy. Considering the severity of the trial the performance of the chronometers generally has been good, the first and second being of special excellence.
The deck watches in the annual trial were separated into two classes, A and B, 76 being entered (by their makers) as A and 24 as B, the trial in positions for the latter (which are intended for ordinary use on board ship) being limited to "dial up" and "pendant up." Of these, 50 have been purchased for the Navy, 33 being classed as A, and 17 as B. The performance of the watches in both classes was very satisfactory and showed a marked improvement on last year, the first watch in class A having the smallest trial number (28.7) since the trials have been instituted.
The next competitive trial of chronometers commences on July 7, and the trial of deck-watches on October 27.
On five days the Greenwich time-ball was not raised on account of the violence of the wind. On one day (January 4) it fell before the proper time as the snow had prevented it from resting properly on the clips. On March 8 the ball was accidentally dropped 18 seconds before the time, and on March 25, 1m before the time. On 1893 May 21 no time signal left the Observatory at 13h owing to a failure in the electric connexions, and on September 14 the Greenwich signal at 13h did not reach the General Post Office, in consequence of alterations which were being made there.
The automatic drop of the Deal time-ball failed on 9 days owing to interruption of the telegraph connexions, and on five days the ball was not raised owing to high wind. The automatic return signal has worked well since it was reintroduced on 1893 May 9, thanks to the attention which Capt. Wrottesley, R.E., of the Post Office Telegraphs, has given to the perfecting of the arrangements, Amongst other improvements a spring platform has been designed and fixed under his supervision by Quarter-Master Sergeant Fawssett, R.E., to take the shock of the ball-drop, which was found to shake the building injuriously, when the cylinder had been cleaned out to allow of a free ball-drop, the air-cushion being ineffective owing to large windage in the cylinder.
The return-signal from the Devonport clock failed on 85 days. Of the remaining 280 days the apparent error of the clock signal (after daily correction of the clock by the help of a time-signal from Greenwich) was under 0.2s on 57 per cent., under 0.5s on 94 per cent., under 1.0s on 98 per cent., and exceeded 1.0s on four occasions.
The return-signal from the Portsmouth clock (similarly corrected by the help of a daily signal from Greenwich) failed on 73 days. The apparent error of the clock-signal was under 0.2s on 77 per cent. of the 292 days of observation, under 0·5s on 97 per cent., under 1.0s on 99 per cent., and exceeded 1.0s on two occasions.
With a view to diminishing the risk of failure in the return-signals, a separate wire with galvanometer has been provided connecting the Observatory with the General Post Office.
The automatic signals from the Westminster clock have been received regularly throughout the year ending 1894 May 10, except on 14 days when the signal failed. The error of the clock was under 0·5s on 24 per cent. of the days of observation, under 1·0s on 41 per cent., under 2.0s on 79 per cent., under 3.0s on 94 per cent., under 4.0s on 98 per cent., and exceeded 4.0s on 5 days.
Longitude Operations: The provisional result of the longitude Paris-Greenwich as determined by the English observers in 1892 June and July, gave 9m 20.84s as the difference between Cassini's meridian of Paris and that of the transit-circle at Greenwich, thus confirming the result 9m 20·85s found in 1888. The provisional result of the determinations by the French observers also confirms exactly their previous result, 9m 21.06s.
On 1893 June 21, Commandant Defforges came to Greenwich to discuss the cause of the discrepancy, and it was suggested that it might be due to an abnormal difference of level between either of the two adjacent observing stations, or to abnormal lateral refractions different at two adjacent stations. Experiments were therefore made in August by means of a floating collimator to measure the inclination of the verticals at the two contiguous longitude stations in the Front Court, with the result that no abnormal deviation could be detected.
Transit observations have also been made on the two piers to determine the difference of longitude between them with the same instruments as were used in the Paris-Greenwich longitude determinations, but though the results obtained up to the present time seem on the whole unfavourable to the existence of an anomaly of this kind, more observations are wanted before this point can be finally decided.
The reduction of the Greenwich-Waterville--Canso-Montreal longitude is completed with the exception of the results for Waterville-Canso, in regard to which there is a discordance of 2¼ seconds between the first and fourth stages, probably due to some misunderstanding of the information supplied by Prof. McLeod. The results have been sent to Prof. McLeod, but at present no sufficient explanation has been afforded. This point, which has been laid aside lately owing to pressure of other matters, is now under consideration. The results for Greenwich-Montreal and Greenwich-Waterville appear to be quite satisfactory.
Mr. Plummer, Director of the Bidston Observatory, Liverpool, having arranged for a determination of the longitude of his Observatory, signals were exchanged on eight nights in August last, Mr. Plummer making time determinations at Liverpool for comparison with the transit-circle observations at Greenwich. He came to Greenwich from January 1 to 9 for determination of personal equation, but cloudy weather prevented observations. He again visited Greenwich from April 20 to May 2, and secured observations on six nights with the small transit in the Transit Pavilion for comparison with the transit-circle observer. It is proposed to have a second exchange of signals shortly.
The Report here presented refers to the year from 1894 May 11 to 1895 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Moveable Property, and Library: -
The South wing of the Physical Observatory, which, as mentioned in the last Report, was completed on 1894 April 20, has been utilized to provide indirectly additional accommodation for chronometers and deck watches, and to relieve the pressure in the Computing Rooms. The ground floor has been fitted up as the Mechanics' workshop, the gas engine and dynamo for electric lighting being placed there, and the room under the Chronometer Room which is thus set free has been fitted up for chronometers. …
As already mentioned the room under the Chronometer Room has been fitted up to give accommodation for the greatly increased number of chronometers and deck watches on trial, and plans have been prepared for a supplementary chronometer oven which is also much wanted.
The principal moveble instruments are thus distributed: -
At Greenwich -
On loan -
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the Oxford University Observatory.
II. - Astronomical Observations: -
Clocks and Chronographs.- The Standard Sidereal clock, which had been going very well till February, stopped on February 27. The escape pivot was found to have become dry and to be cut. The clock was repaired by Messrs. E. Dent & Co., and brought into use again on March 6. During the interval the Clock Hardy was used as the Standard.
The Clock Dent 2016 was taken from the Lassell Dome on 1894 October 25 and placed in the Lower Chronometer Room.
The Clock Dent 2009 was placed in the 36-feet dome on 1894 July 6, and Dent 2014 in the South Wing of the New Physical Observatory.
The mean solar clock Dent 2012, which had been adapted in 1893 to replace the electrical clock Shepherd, worked satisfactorily from 1894 May 4, when a new set of contacts was supplied, to August 27, when it again failed to drive the sympathetic dials in the Observatory, the contacts being burnt through sparking from the large batteries required. It was then arranged that a suitable relay should be supplied by the Post Office, and this has now been provided but has not yet been brought into action by the Post Office Authorities. Meanwhile the clock Shepherd has been used as mean solar clock, though its large and variable rate makes it unsuitable for sending out accurate hourly time signals.
VII. - Chronometers, Time Signals, and Longitude Operations:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 290 (179 box chronometers, 26 pocket chronometers, and 85 deck-watches). In addition to these, there are on trial for the Indian Government, 2 two-day and 2 pocket chronometers for the Mathematical Instrument Office, Calcutta, and 4 eight-day and 1 pocket chronometer for Colaba Observatory. In the year ending 1895 May 10, the average daily number of chronometers and deck-watches being regularly rated was 364; the total number received was 1,048, the total number issued 1,026, and the number sent for repair 499. These include 35 box chronometers, 10 pocket chronometers, and 1 deck-watch tested for the Indian Government.
For the annual trial of chronometers, which lasted for 29 weeks, with a range of temperature from 40° to 106°, 72 chronometers were sent in, and of these, 42 have been purchased for the Navy. The performance of the chronometers generally was remarkably good, and showed a very decided improvement on previous years. The first chronometer was an exceptionally fine one, and the second and third performed better than any chronometer in the last three trials.
The deck-watches in the annual trial were separated into two classes, A and B, 129 being entered (by their makers) as A, and 31 as B, the trial in positions for the latter being limited to "dial up" and "pendant up." Of these, 36 have been purchased for the Navy, 29 being classed as A and 7 as B. The performance of the watches in both classes was fully up to the standard of last year's trial. 11 non-magnetic watches were entered in class A, and 6 in class B, but their performance was unsatisfactory. The next competitive trial of chronometers commences on July 6, and the trial of deck-watches on October 26.
On four days the Greenwich time-ball was not raised on account of the violence of the wind. On one day (January 23) the ice and snow on the mast held the ball fa that it did not fall when the clips were released, and some difficulty was experienced in forcing it down. On April 22 the chain broke as the ball was being raised, and the ball was not raised again till May 2, after a new chain had been obtained and the cylinder which acts as an air cushion had been cleaned. This was found to be very rusty, and on further examination it was discovered that the upper portion of the wooden framework of the ball was rotten, and allowed the rain to run down the mast into the cylinder. The ball was not raised on May 10, and arrangements were made for its thorough repair.
On 1894 November 12 no time signal left the Observatory at 13h owing to a failure in the electric connections, and on 1895 January 20 the Greenwich signal at 13h did not reach the General Post Office.
The automatic drop of the Deal time-ball failed on seven days owing to interruptions of the telegraph connexions, and on seven days the ball was not raised owing to high wind.
The return-signal from the Devonport clock failed on 46 days. The apparent error of the clock signal (after daily correction of the clock by aid of a time-signal from Greenwich) was under 0.2s on 46 per cent. of the 319 days of observation, under 0.5s on 97 per cent., and never exceeded 1.0s.
The return -signal from the Portsmouth clock (similarly corrected by the help of a daily signal from Greenwich) failed on 45 days. The apparent error of the clock-signal was under 0.2s on 59 per cent. of the 320 days of observation, under 0.5s on 94 per cent., under 1.0s on 98 per cent., and exceeded 1.0s on six occasions.
It was stated in the last Report that to diminish the risk of failure in the return-signals, a separate wire with galvanometer had been provided connecting the Observatory with the General Post Office. The number of failures has decreased since the last Report: for Deal from 9 to 7; for Devonport from 85 to 46; for Portsmouth from 73 to 45.
The automatic signals from the Westminster clock have been received regularly throughout the year ending 1895 May 10, except on 14 days when the signal failed. The apparent error of the clock was under 0.5s on 20 per cent. of the days of observation, under 1.0s on 41 per cent., under 2.0s on 75 per cent., under 3.0s on 94 per cent., under 4.0s on 94 per cent., and exceeded 4·0s on two days.
Longitude Operations. - The discordance of 2¼ seconds between the two determinations of the section Waterville-Hazel Hill of the Montreal longitude, referred to in last year's Report, has been traced to a misapprehension in the numeration of the seconds. When this was corrected, and the final determinations of clock error supplied by Professor McLeod adopted, the results showed a very satisfactory agreement throughout. A draft copy for press, showing the history and results of this work, has been prepared, and will be published shortly.
Transit observations by pairs of observers have been made on ten nights during the past year to determine the difference of longitude between the contiguous longitude stations in the Front Court with the same instruments as were used in the Paris-Greenwich longitude determinations. The observations on only six of these nights have been reduced as yet. These do not show any anomalous difference of longitude.
The Report here presented refers to the year from 1895 May 11 to 1896 May 10, and exhibits the state of the Observatory on the last-named day.
I. - Buildings and Grounds, Moveable Property, and Library:-
Provision has been made for the supplementary chronometer oven referred to in the last Report, and it is now being made.
The principal moveable instruments are thus distributed:-
At Greenwich- [no clocks mentioned]
On loan-
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the Oxford University Observatory.
II. - Astronomical Observations:-
Clocks and Chronographs. - The Standard Sidereal clock, which was repaired in 1895 March, has gone very well throughout the year. As illustrating the performance of the clock its error is given below for the beginning and middle of each month from October 1 to May 1:-
| 1895 | Ocober | 1 | 4.50s slow | |
| October | 16 | 4.72s slow | ||
| November | 1 | 4.81s slow | ||
| November | 15 | 5.54s slow | ||
| December | 1 | 6.22s slow | ||
| December | 16 | 6.15s slow | ||
| 1896 | January | 1 | 5.60s slow | |
| January | 16 | 5.40s slow | ||
| February | 1 | 5.42s slow | ||
| February | 14 | 5.10s slow | ||
| March | 1 | 5.05s slow | ||
| March | 16 | 4.51s slow | ||
| April | 1 | 4.65s slow | ||
| April | 15 | 4.99s slow | ||
| May | 1 | 4.60s slow |
The Clock Hardy (in the Transit-circle room) was repaired in March, and the Clock Earnshaw (in the Sheepshanks dome) in April.
The mean solar clock Dent 2012 has been in use for driving the sympathetic dials in the observatory through It relay, and for sending the hourly time-signals to the General Post Office, except during the months of October and November, when the clock Shepherd was used.
VII.- Chronometers, Time Signals, and Longitude Operations:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 215 (127 box chronometers, 31 pocket chronometers, and 57 deck-watches). In addition to these, there are on trial for the Indian Government, 18 box chronometers and 1 pocket chronometer. In the year ending 1896 May 10, the average daily number of chronometers and deck-watches being rated was 395; the total number received was 958, the total number issued 1,002, and the number sent for repair 477. These include 22 box chronometers, and 4 pocket chronometers, for the Indian Government, and 5 deck-watches for the Crown agents for the Colonies.
For the annual trial of chronometers, which lasted for 29 weeks, with a range of temperature from 42° to 105°, 83 chronometers were sent in, and of these, 55 have been purchased for the Navy. The performance of the chronometers generally is remarkably good and sustains the improvement shown last year. The relaxation in 1892 of the rule limiting the entry for each maker to two chronometers seems to have worked well in securing a large supply of good chronometers.
The deck-watches in the annual trial were separated into two classes, A and B, 92 being entered (by their makers) as A, and 37 as B, the trial in positions for the latter being limited to "dial up" and "pendant up." Of these, 51 have been purchased for the Navy, 42 being classed as A and 9 as B. The performance of the watches was fully up to the standard of previous years. Four of the watches entered in class B are non-magnetic, and one of these was purchased. The next competitive trial of chronometers commences on July 4, and the trial of deck-watches, class A, on October 24. It has been decided to discontinue the trial and purchase of class B deckwatches.
As mentioned in the last Report, the Greenwich time-ball required extensive repairs, which were carried out in May and June, and the ball was not raised between the dates May 10–May 28 and June 6–June 25. On five days it was not raised on account of the violence of the wind. It failed to drop on January 2 and February 2, when the failure was traced to wear in the trigger levers, which were taken off and repaired. On January 12 (Sunday) the ball was not dropped through inadvertence in making the connections.
There were two failures in the Greenwich time signal at 13[h] on 1895 May 14 and 1896 January 12, respectively, owing to a break in the electric connections.
The automatic drop of the Deal time-ball failed on six days owing to interruptions of the telegraph connections and once through inadvertence in setting the trigger. On ten days the ball was not raised owing to high wind.
The return-signal from the Devonport clock failed on 27 days. The apparent error of the clock signal (after daily correction of the clock by aid of a time-signal from Greenwich) was under 0.2s on 65 per cent. of the 337 days of observation, under 0.5s on 97 per cent., and never exceeded 1.0s.
The return-signal from the Portsmouth clock (similarly corrected by the help of a daily signal from Greenwich) failed on 50 days. The apparent error of the clock signal was under 0.2s on 34 per cent. of the 316 days of observation, under 0.5s on 95 per cent., under 1.0s on 99 per cent., and exceeded 1.0s on three occasions.
The automatic signals from the Westminster clock have been received regularly throughout the year ending 1896 May 10, except on 46 days when the signal failed. The apparent error of the clock was under 0.5s on 37 per cent. of the days of observation, under 1.0s on 56 per cent., under 2.0s on 90 per cent., under 3.0s on 93 per cent., under 4.0s on 98 per cent., and exceeded 4.0s on three days.
Longitude Operations. - The Indian Government having decided to make a re-determination of the longitude of Madras viâ Potsdam and Teheran, Capt. Burrard, R.E., and Capt. Lenox Conyngham, R.E., made the requisite observations for the section Greenwich-Potsdam in June and July last, their transit instrument being mounted in the Transit Pavilion in the Front Court.
IX.-General Remarks:-
… But, with the diminished staff of Assistants, it has been necessary to suspend the spectroscopic observations, and it has not been found practicable to carry out supplementary investigations such as the proposed determination of the longitude of Killorglin (at the western end of the great European arc of longitude), and the discussion of discordances in the Paris longitude determinations referred to in previous Reports. It is hoped that these may be undertaken next year.
The Report here presented refers to the year from 1896 May 11 to 1897 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Moveable Property, and Library:-
The principal moveable instruments are thus distributed:-
At Greenwich-
On loan-
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
II.-Astronomical Observations:-
Clocks and Chronographs:- The Standard Sidereal clock dropped 4 seconds on October 10 and on October 21 was found to be stopping. The contact springs were released but without effect. The pendulum was started again and the clock has since gone satisfactorily.
The electric dials sympathetic with the Mean Solar clock and used in the various rooms of the Observatory are being reconstructed, a single armature being substituted for an oscillating magnet, and one battery being used instead of two. All the dials with the exception of the Gate Clock and the dial in the Ball Lobby are now worked on the new system. Four electric dials have been purchased for use in the new Physical Observatory.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 288 (166 box chronometers, 29 pocket chronometers, and 93 deck-watches). In addition to these, there are on trial for purchase by the Indian Government 42 box chronometers, and 2 box chronometers are being tested after repair. In the year ending 1897 May 10 the average daily number of chronometers and deck-watches being rated was 446; the total number received was 1,220, the total number issued 1,124, and the number sent for repair 519. These include 8 box chronometers and 3 pocket chronometers for the Indian Government. The trial of 18 chronometers for the Indian Government, mentioned in the last Report, was finished in 1896 June, and 6 of the chronometers were purchased.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 42° to 106°, 97 chronometers were sent in, and of these, 54 have been purchased for the Navy. The performance of the chronometers is remarkably good and sustains the improvement shown in recent years.
The deck-watches in the annual trial were this year confined to class A, and were tried in positions "dial up," "pendant up," "pendant right" and "pendant left"; 154 were entered and of these, 30 were purchased for the Navy. The performance of the watches was above the standard of recent years. The difficulty experienced in securing accurately divided seconds dials has been met in some cases by centre-seconds dials, which have been found to be as reliable as the others while the divisions are larger and more accurate. There has also been a marked increase of "tourbillon" watches this year. The next competitive trial of chronometers commences on July 3, and the trial of deck-watches on October 23.
The Greenwich time-ball was not raised on five days during the year owing to the violence of the wind. Twice it was dropped accidentally before 13h, once by a false signal and once because the piston did not rest properly on the clips. It was raised and dropped again at 14h on these days.
There were no failures in the Greenwich time signal at 13h, but on Sunday, August 9, it was 1.0s late, Sunday, November 8, 0.8s late, and on Good Friday, Apri11 6, it was 0.5s early.
The automatic drop of the Deal time-ball failed on two days owing to interruptions of the telegraph connections. On 10 days the ball was not raised owing to high wind.
The return signal from the Devonport clock failed on 24 days, and could not be observed on 13 days owing to interruption by telegraph signals. The apparent error of the clock-signal (after daily correction of the clock by aid of a time-signal from Greenwich) did not exceed 0.2s on 72 per cent. of the 323 days of observation, did not exceed 0.5s on 97 per cent., and never exceeded 1.0s.
The return signal from the Portsmouth clock (similarly corrected by the help of a signal from Greenwich) failed on 59 days, and could not be observed on 7 days owing to interruption by telegraph signals. The apparent error of the clock-signal did not exceed 0.2s on 81 per cent. of the 292 days of observation, did not exceed 0.5s on 95 per cent., and never exceeded 1.0s.
The automatic signal from the Westminster clock have been received throughout the year, except on 31 days, when the signal failed. The apparent error of the clock was not greater than 0.5s on 34 per cent. of the days of observation, not greater than 1.0s on 55 per cent., not greater than 2.0s on 80 per cent., not greater than 3.0s on 92 per cent., and once exceeded 4.0s.
Longitude Operations. - Observations have been continued to determine the difference of Iongitude between the stations in the Front Court with the same instruments as were used in the Paris-Greenwich longitude determinations. Complete determinations have been secured on six nights, and these observations, as well as those made on eight nights in the winter of 1894-95, have all been reduced. The difference of longitude is found to be + 0.007s when the level is determined from nadir observations and + 0.107s when it is obtained from the striding level, the individual results being more accordant when reduced with the level determination obtained from the nadirs. The geodetic difference of longitude is + 0.021s, which agrees sufficiently well with the astronomically determined difference. As the portable transit instruments have now been satisfactorily tested, it is hoped that the determination of the longitude of Killorglin or some other suitable station at the western extremity of the great European arc of longitude (to which reference has been made in previous reports) maybe undertaken next year, with a view to eliminating the probable local attraction at Valentia and Waterville, the stations which have been used for longitude determinations.
It may be mentioned here that the Astronomer Royal went to Japan (taking with him the Thompson 9-inch photographic, telescope to photograph the corona on a large scale) and Mr. Maunder and Mr. Crommelin to Norway, to observe the total eclipse of the Sun on August 9. No observations during totality were obtained at either station owing to cloud.
The Report here presented refers to the year from 1897 May 11 to 1898 May 10, and exhibits the state of the Observatory on the last-named day.
I.- Buildings and Grounds, Movable Property, and Library-
The principal movable instruments are thus distributed:-
At Greenwich -
On loan -
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
II.-Astronomical Observations:-
Clocks and Chronographs. - The Standard Sidereal clock dropped seconds on several days in September. The contact springs were taken off and cleaned September 12-16, and the clock has gone satisfactorily since that date.
The electric dials sympathetic with the Mean Solar clock have been reconstructed according to the plan mentioned in the last Report. Electric dials have now been fitted up in the North and South rooms of the New Physical Observatory, and the wiring arrangements have been made so that similar dials can be fitted up in the East and West rooms as soon as they are ready for occupation. New wires have also been laid to enable the Sidereal Standard clock to work sympathetic dials, or to register on chronographs in the New Altazimuth building and in the Thompson Equatorial Dome.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 372, viz., 252 box chronometers, 32 pocket chronometers, and 88 deck-watches. In addition to these, there are on trial for the Indian Government 3 box chronometers, and 3 pocket chronometers, and 3 box chronometers are being tested after repair. In the year ending 1898 May 10 the average daily number of chronometers and deck-watches being rated was 463; the total number received was 1,202, the total number issued 1,135, and the number sent for repair 463. These include 11 box chronometers, 6 pocket chronometers, and 1 deck-watch for the Indian Government. The trial of 42 chronometers for the Indian Government, mentioned in the last Report, was finished in 1897 June, and 17 of the chronometers wore purchased.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 41° to 102°, 98 chronometers were sent in, and or these, 51 have been purchased for the Navy, and 3 for the Indian Government. The performance of the chronometers is remarkably good, and the improvement shown in recent years is maintained.
The deck-watches in the annual trial were confined to class A, and were tried in the positions "dial up," "pendant up," "pendant right" and "pendant left"; 150 were entered, and of these, 37 were purchased for the Navy. The performance of the watches was very satisfactory. In consequence of the difficulty of securing accurately divided seconds dials, the Admiralty have offered an extra premium for watches with centre-seconds dials, as these have been found as reliable as others, while the divisions are larger and more accurate. There were 15 "tourbillon" watches in the annual trial. The next competitive trial of chronometers commences on July 2, and of deck-watches on October 2.
The Greenwich time-ball was not raised on five days during the year owing to the violence of the wind. On October 10 the ball fell 2m before the time signal. It was raised again and dropped correctly. On February 12 and March 1 the ball fell before 13h. It was raised and dropped at 14h on these days. Examination of the cause of the ball dropping before the signal on these days showed that the piston was much worn where it rests on the clips. The piston, clips, and machinery in general were completely overhauled and put in good order. On two days during the repairs, March 17 and 18, the ball was not raised.
There were no failures in the Greenwich time signal at 13h but on January 14 it was 0.5s late.
The automatic drop of the Deal time-ball failed on five days owing to interruptions of the telegraph connections, on one day owing to a defect in the relay, and on one day owing to a defect in the machinery. A new cog-wheel was put on the winding apparatus in July. On 10 days the ball was not raised owing to high wind. Mr. William Newby, the attendant in charge of the time-ball, retired, owing to failing health, on January 24, and the care of the time-ball was handed over to Mr. J. G. Hayward on that date. In connection with this change stock was taken and an inventory made of the Government property in the Time-Ball Tower, by Mr. Bowyer, the Established Computer attached to the Time Department.
The return signal from the Devonport clockk failed on 56 days (18 of these were Sundays), and could not be observed on 11 days owing to interruption by telegraph
signals. The apparent error of the clock-signal (after daily correction of the clock by aid of a time signal from Greenwich) did not exceed 0.2s on 89 per cent. of the 291 days of observation, did not exceed 0.5s on 99 per cent., and never exceeded 1.0s.
The return signal from the Portsmouth clock (similarly corrected by the help of a signal from Greenwich) failed on 50 days (30 of these were Sundays), and could not be observed on 7 days owing to interruption by telegraph signals. The apparent error of the clock-signal did not exceed 0.2s on 85 per cent. of the 298 days of observation, did not exceed 0.5s on 98 per cent., and exceeded 1.0s on one occasion.
The automatic signals from the Westminster clock have been received throughout the year, except on 38 days, when the signal failed. The apparent error of the clock was not greater than 0.5s on 28 per cent. of the days of observation, not greater than 1.0s on 54 per cent., not greater than 2.0s on 85 per cent., not greater than 3.0s on 94 per cent., and never exceeded 4.0s.
A mean solar clock made for the Perth Observatory, W. Australia, was under examination from 1897 September to 1898 May. It is fitted with hourly and seconds contacts and with galvanic apparatus for correction of its error. It has given considerable trouble, but is now ready for use.
Provision has been made this year for the determination of the longitude of Killorglin (Co. Kerry) or some other suitable station in the west of Ireland, as supplementing the longitude determinations of Valentia and Waterville in connection with the western extremity of the great European arc of longitude. It is proposed to undertake this work in the autumn, the portable transits which are to be used having now been thoroughly tested by longitude observations made at two contiguous stations in the Front Court of the Observatory, as mentioned in the last Report.
It may be mentioned here that the Astronomer Royal (taking with him the Thompson 9-inch photographic telescope) and Mr. Maunder went to India to observe the total eclipse of the Sun on January 22. Successful large scale photographs of the Corona were obtained with the Thompson photographic telescope, and also a series of photographs of the partial eclipse for determination of the Moon's position relatively to the Sun, the local time and the longitude of the station being determined by Major Burrard, R.E., and Lieutenant Crosthwait, R.E., of the Indian Survey.
The Report here presented refers to the year from 1898 May 11 to 1899 May 10, and exhibits the state of the Observatory on the last-named day.
I. - Buildings and Grounds, Movable Property, and Library:-
The room formerly used as the Astronomer Royal's Official Room has been converted into an additional Chronometer Room, and has been fitted up with long tables or shelves to accommodate 140 chronometers.
The principal movable instruments are thus distributed:-
At Greenwich-
On loan -
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
II. - Astronomical Observations:-
Clocks and Chronographs. - New contact wheels were fitted to the Mean Solar Clock Dent 2012 in December, the time signals being sent during the alterations by the Clock Shepherd.
Electric dials, sympathetic with the Mean Solar Clock, have been placed in the East and West rooms of the. new building, similar to those in the North and South rooms.
Electric bells have also been fitted up to give an hourly time signal from the Mean Solar Clock. The Clock Graham 1. was removed from the old Altazimuth dome and fixed in the new Altazimuth dome on March 17. The Clock Dent 2016 has been placed in the dome of the Thompson Equatorial and is used to control the driving clock of the Equatorial. The alternate seconds contact wheel was replaced by one giving contacts each second in March.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 374, viz., 246 box chronometers, 30 pocket chronometers, and 98 deck-watches. In addition to these there are 5 box chronometers on trial for purchase by the Indian Government, and 10 box chronometers and 1 pocket chronometer are being tested after repair. In the year ending 1899 May 10, the average daily number of chronometers and deck-watches being rated was 499; the total number received was 1,090, the total number issued 1,087, and the number sent for repair 466. These include 32 box chronometers and 1 pocket chronometer for the Indian Government. One eight-day box chronometer and one pocket chronometer have been purchased, after trial, for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 46° to 108°, 103 chronometers were sent in, and of these 50 were purchased for the Navy and 4 for the Indian Government, The performance of these chronometers was fully up to the high standard obtained in recent years.
The deck-watches in the annual trial were tried in the positions "dial up," "pendant up," "pendant right," and "pendant left"; 145 were entered, and of these 43 were purchased for the Navy. The performance of the watches was very satisfactory. Among the watches sent for trial were 5 with centre seconds dials of which 4 were purchased. There were 42 "tourbillon" watches in the annual trial. The next competitive trial of chronometers commences on July 1, and of deck-watches on October 21.
As in all probability the chronometers and deck-watches required for the Navy will, in the course of the next two or three years, reach a number which is sufficient for all practical purposes, it is unlikely that any large annual number will be required after 1902. The purchases will then be merely to replace unserviceable instruments. Chronometer and watch makers have been notified accordingly.
The Greenwich time-ball was not raised on five days during the year, owing to the violence of the wind. On May 19, June 30, and December 7, the ball did not drop at 13h owing to the failure of the time signal. It was raised and dropped at 14h on these days.
There were 3 failures in the Greenwich time signal at 13h due to failure in the electric contacts, and on October 10 it was 0.5s late.
The automatic drop of the Deal time-ball failed on 8 days owing to interruptions of the telegraph connexions, and on one day owing to a defect in the relay at Deal. On 8 days the ball was not raised owing to high wind.
The return signal from the Devonport clock failed on 36 days (of which 9 were Sundays), and could not be observed on 14 days owing to interruption by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich) did not exceed 0.2s on 74 per cent. of the 308 days of observation, did not exceed 0.5s on 95 per cent., and never exceeded 1.0s.
The return signal from the Portsmouth clock (similarly corrected by the help of a time signal from Greenwich) failed on 53 days (28 of these being Sundays), and could not be observed on 4 days owing to interruption by telegraph signals. The apparent error of the clock signal did not exceed 0.2s on 82 per cent. of the 301 days of observation, did not exceed 0.5s on 98 per cent., and exceeded 1.0s on two occasions.
The automatic signals from the Westminster clock have been received throughout the year except on 48 days, when the signal failed. On 10 days the signal could not be observed owing to interruption by telegraph signals. The apparent error of the clock was not greater than 0.5s on 25 per cent. of the days of observation, not greater than 1.0s on 44 per cent., not greater than 2.0s on 74 per cent., not greater than 3.0s on 95 per eent., and exceeded 4.0s on one occasion.
The longitude of Killorglin, at the head of Dingle Bay, Ireland, was determined in October and November. The station was selected in order to eliminate, as far as possible, the effect of local attraction at Valentia and Waterville, both of which longitude stations are situated between the Atlantic on the West and a mountain mass on the East. The observations at Killorglin and Greenwich were made by Mr. Dyson and Mr. Hollis with the portable transits D. and E., and were divided into three groups of three, six and three full nights (or their equivalents in half nights), the observers with their instruments being interchanged between the first and second, and again between the second and third groups. Altogether signals for comparison of clocks were interchanged on 44 nights, clock errors were determined at Greenwich on 26 nights and at Killorglin on 22 nights, observations at both stations being obtained on 15 of these nights. The reduction of the observations is practically complete.
A desire has been expressed by the International Geodetic Association for a re-determination of the longitude of Paris-Greenwich in view of the discordance in the results found by the French and English observers respectively in the two determinations in 1888 and 1893 [1892], and the Council of the Paris Observatory have recommended that this work should be undertaken in' concert with Greenwich Observatory. As a preliminary to the actual longitude operations it seems essential that the instruments to be used by both parties of observers should be thoroughly tested at contiguous stations.
The Report here presented refers to the year from 1899 May 11 to 1900 May 10, and exhibits the state of the Observatory on the last-named day.
I. - Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:-
At Greenwich-
On loan-
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government marine chronometers and deck-watches l!-0w being tested at the Observatory is 360, viz., 245 box chronometers, 33 pocket chronometers, and 82 deck-watches. In addition to these there are 2 pocket chronometers on trial for purchase by the Indian Government, and 4 box chronometers and 1 pocket chronometer are being tested after repair. In the year ending 1900 May 10, the average daily number of chronometers and deck-watches being rated was 535; the total number received was, 1,145, the total Dumber issued 1,172, and the number sent for. repair 470. These include 26 box chronometers and 3 pocket chronometers for the Indian Government. During the year there have been on trial for purchase by the Indian Government 7 box. chronometers and 14 pocket chronometers. From these and from the annual trial 13 box and 8 pocket chronometers have been purchased for India.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 43° to 105°, 85 chronometers were sent in, and of these 37 were purchased for the Navy and 5 for the Indian Government. The performance of these chronometers was good, but not quite up to the high standard of recent years.
The deck-watches in the annual trial were tried in. the positions "dial up," "pendant up," "pendant right," and "pendant left"; 131 were- entered, and of these 22 were purchased for the Navy .
Among the watches sent for trial were 15 with centre seconds dials, of which 4 were purchased. There were 78 "tourbillon" watches in the annual trial. The performance of the deck-watches generally was somewhat below the standard, and the number purchased for the Navy was not so large as it would otherwise have been. The next competitive trial of chronometers commences on July 7, and of deck-watches on October 27.
The Greenwich time-ball was not raised on five days during the year, owing to the violence of the wind. On October 22 it was dropped in error.
There were 4 failures in the Greenwich time signal at 13h due to failure in the electric contacts.
The automatic drop of the Deal time-ball failed on 17 days owing to interruptions of the telegraph connexions, and on one. day owing to a defect in the relay at Deal. On 6 days the ball was not raised owing to high wind.
The return signal from the Devonport clock failed on 45 days (of which 20 were Sundays), and could not be observed on 24 days owing to interruption by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich) did not exceed 0.2s on 88 per cent. of the 292 days of observation, did not exceed 0.5s on 97 per cent., and never exceeded 1.0s
The return signal from the Portsmouth clock (similarly corrected by the help of a time signal from Greenwich) failed on 79 days (30 of these being Sundays), and could not be observed on 3 days owing to interruption by telegraph signals. The apparent error of the clock signal did not exceed 0.2s on 78 per cent. of the 278 days of observation, did not exceed 0.5s on 97 per cent., and exceeded 1.0s on one occasion.
The automatic signals from the Westminster clock have been received throughout the year except on 13 days. when the signal failed. On 3 days the signal could not be
observed owing to interruption by telegraph signals. The apparent error of the clock was not greater than 0.5s on 19 per cent. of the days of observation, not greater than 1.0s on 41 per cent., not greater than 2.0s on75 per cent., not greater than 3.0s on 87 per cent., and exceeded 4.0s on five occasions.
The publication of the various determinations of longitude made in the years 1888 to 1898 has now been taken in hand, viz.: Paris, in 1888; Paris (re-determination), in 1892; Montreal, Canso, and Waterville, in 1892; Killorglin, in 1898; and observations at Greenwich at contiguous stations in the years 1893 to 1897, to test the transit instruments used in the various longitude operations. During the past year the observations made in 1892 for re-determination of the Paris longitude have been re-examined, especially in regard to the adoption of instrumental errors, and the copy for press has been prepared. This, as well as the copy for press for the determination made in 1888, is now ready for the printer.
For the longitude Greenwich-Waterville-Canso-Montreal, the copy for press for the first stage, in April and May 1892, is ready, and that for the second stage, in August and September 1892, is in progress.
An expedition to observe the total solar eclipse of May 28 having been sanctioned by the Admiralty, the Astronomer Royal, with Mr. Dyson and Mr. Davidson, left for Ovar, in Portugal, on May 11, taking with them the Thompson 9-inch photographic telescope, with new 4-inch enlarging lens for large-scale photographs of the corona, a pail' of photographic spectroscopes with heliostat, lent by Captain Hills, for photographing the spectrum of the flash and of the corona, and a double camera, on one of the photo-heliograph mountings, with lenses of 4 inches and 2t inches aperture for photographing the coronal streamers.
The Report here presented refers to the year from 1900 May 11 to 1901 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:-
At Greenwich-
On loan--
Clocks - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 379, viz., 242 box chronometers, 27 pocket chronometers, and 110 deck-watches. In addition to these 6 box chronometers and 1 pocket chronometer are being tested after repair for the Indian Government.
In the year ending 1901 May 10, the average daily number of chronometers and deck-watches being rated was 504; the total number received was 1,118, the total number issued 1,088, and the number sent for repair 479. These, include 23 box chronometers and 1 pocket chronometer for the Indian Government. During the year there have been on trial for purchase by the Indian Government 8 box chronometers from which 3 have been selected for purchase.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 39° to 104°, 76 chronometers were sent in, 20 being rejected in the course of the trial on account of the difference between one week's rate and the next having exceeded 12 seconds. Out of the remaining 56 chronometers 40 were purchased for the Navy and 3 for the Indian Government. The performance of the chronometers shows a very satisfactory improvement on that of last year, and compares favourably with the trials of 1896-7-8.
The deck-watches in the annual trial were tried in the positions "dial up," "pendant up," "pendant right," and "pendant left"; 147 were entered, and of these 30 were purchased for the Navy, and one for the Indian Government. Among the watches sent for trial were 36 with centre seconds dials, of which 9 were purchased. There were 82 "tourbillon" watches in' the annual trial. The performance of the deck-watches generally was somewhat below the standard, which may be partly attributed to a rather more severe trial, a very cold week having immediately succeeded the trial in heat. The next competitive trial of chronometers commences on July 6, and of deck-watches on October 26.
The Greenwich time-ball was not raised on three days during the year, owing to the violence of the wind. On June 27, December 16, and February 3 the ball failed to drop at 13h, and on February 4 it dropped one minute too soon. The time of ball-drop was also erroneous on the days when the time signal at l3h was faulty.
There were failures on June 27 and February 3 in the Greenwich time signal at 13h due to failure in the electric contacts. The error of the 13h signal was inappreciable except on the following dates, viz.: July 29 (Sunday), 1s late; November 18 (Sunday), 4s late; March 3 (Sunday), 9s early; March 25, Is late. Much trouble has been caused by rats gnawing the telegraph wires passing under the floors in the Observatory.
The automatic drop of the Deal time-ball failed on 7 days owing to interruptions of the telegraph connexions, and on one day owing to a defect in the relay at Deal. On 11 days the ball was not raised owing to the violence of the wind.
The return signal from the Devonport clock failed on 56 days (of which 16 were Sundays), and could not be observed on 26 days owing to interruption by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich) did not exceed 0.2s on 83 per cent. of the 278 days of observation, did not exceed 0.5s on 95 per cent., and exceeded 1.0s on one occasion only.
The return signal from the Portsmouth clock (similarly corrected by the help of a time signal from Greenwich) failed on 71 days (31 of these being Sundays), and could not be observed on 7 days owing to interruption by telegraph signals. The apparent error of the clock signal did not exceed 0.2s on 81 per cent. of the 283 days of observation, did not exceed 0.5s on 94 per cent., and exceeded 1.0s on two occasions.
The automatic signals from the Westminster clock have been received throughout the year except on 8 days, when the signal failed, and from August 12 to September 19 when the clock was under repair. The apparent error of the clock was not greater than 0.5s on 25 per cent. of the days of observation, not greater than 1.0s on 45 per cent., not greater than 2.0s on 72 per cent., not greater than 3.0s on 85 per cent., and exceeded 4.0s on 12 occasions.
The publication of the various determinations of longitude made in the years 1888 to 1898, has been pushed forward as much as circumstances would allow. The determination Greenwich-Paris made in 1888 is printed, and the manuscript for that made in 1892 is in the printer's hands.
Arrangements have been made for a re-determination of the Greenwich-Paris longitude in conjunction with observers from the Paris Observatory, two of the four portable transit instruments used in former longitude work being available for the French observers, and the other two for the English. These instruments have been cleaned and put in good order, and another pair of stands with reversing apparatus is being made by Messrs. Troughton and Simms,. there being only one pair of such stands at present. It has been arranged with M. Lœwy that the first part of the longitude observations shall be made in October next, and the second part in the spring of 1902.
A proposal to send out two observers from the Royal Observatory to observe the total solar eclipse of May 18 in Mauritius and Sumatra respectively having been approved by the Admiralty, Mr. Dyson left for Sumatra on March 12, and Mr. Maunder for Mauritius on March 23, taking with them the instruments mentioned on page 5 of this Report, which were specially prepared for observation of the eclipse. Mr. J. J. Atkinson, who rendered valuable assistance in observing the eclipse in Portugal last year, has again volunteered to go out with Mr. Dyson to assist him in his observations in Sumatra. It has been arranged that Mr. Maunder shall carry out a programme of observation in concert with the Director of the Mauritius Observatory, Mr. Claxton, who was formerly on the Greenwich staff.
The Report here presented refers to the year from 1901 May 11 to 1902 May 10, and exhibits the state of the Observatory on the last-named day.
I. -Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments arc thus distributed:-
At Greenwich-
On loan-
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government murine chronometers and deck-watches now being tested at the Observatory is 450, viz., 263 box chronometers, 41 pocket chronometers, and 146 deck-watches. In addition to these 3 chronometers and 1 pocket chronometer are being tested after repair for the Indian Government.
In the year ending 1902 May 10, the average daily number of chronometers and deck-watches being rated was 557; the total number received was 1,258, the total number issued was 1,183, and the number sent for repair 570. These include 35 box chronometers and 2 pocket chronometers for the Indian Government. During the year there have been on trial for purchase by the Indian Government 8 box chronometers of which 3 have been selected for purchase. Two pocket chronometers have also been purchased for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks, with n range of temperature from 44°to 106°, 70 chronometers were sent in, 18 being rejected in the course of the trial on account of the difference between ono week's rate and the next having exceeded 12 seconds. Out of the remaining 52 chronometers 31 were purchased for the Navy and 2 for the Indian Government. The performance of the chronometers was very satisfactory, fully maintaining the standard of recent years.
The deck-watches in the annual trial were tried in. the positions "dial up," "pendant up," "pendant right," and "pendant left"; 146 of these were entered, and of these 42 were purchased for the Navy. Among the watches sent for trial were 34 with centre seconds dials, of which 9 were purchased. There were 85 " tourbillon" watches in the annual trial. The performance of the deck-watches generally shows a great improvement on the last two years, and is, on the whole, better than in any preceding year. The next competitive trial of chronometers commences on July 5, and of deck-watches on October 25.
The Greenwich time-ball was not raised on two days during the year, owing to the violence of the wind. On June 18 the ball did not drop at 13h, owing to an interruption in the electric connexions. The time of ball-drop was also erroneous on the days when the time signal at l3h was faulty.
The Greenwich time signal at 13h failed on June 18 owing to the fault in the electric connexions referred to in the last paragraph. The error of the signal at l3h was inappreciable except on the following dates, viz.: December 1 (Sunday), 0.6s early; January 5 (Sunday), 0.5s early; March 16 (Sunday), 1.0s early; April 27 (Sunday), 50s late.
The automatic drop of the Deal time-ball failed on 5 days owing to interruptions of the telegraphic connexions. On 7 days the ball was not raised owing to the violence of the wind. On one day the ball was dropped 10s too soon; it was raised again at 14h and dropped by hand.
The return signal from the Devonport clock failed on 30 days (of which 14 were Sundays), and could not be observed on 17 days owing to interruption by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0.2s on 90 per cent. of the 311 days of observation, did not exceed 0.5s on 97 per cent., and exceeded 1.0s on eight occasions.
The return signal from the Portsmouth clock (similarly corrected by the help of a time signal from Greenwich) failed on 43 days (24 of these being Sundays), and could not be observed on 9 days owing to interruption by telegraph signals. The
apparent error of the clock signal did not exceed 0.2s on 81 per cent. of the 303 days of observation, did not exceed 0.5s on 99 per cent., and exceeded 1.0s on four occasions.
The automatic signals from the Westminster dock have been received throughout the year except on 5 days, when the signal failed. The apparent error of the clock was not greater than 0"5 on 28 per cent. of the days of observation; not greater than 1"0 on 56 per cent., not greater than 2"0 on 88 per cent., not greater than 3"0 on 97 per cent., and exceeded 4"'0 on 12 occasions.
Longitude Operations. - The first stage of the re-determination of the Greenwich-Paris longitude, referred to in the last Report, was, after consultation with M. Lœwy, deferred to the spring of this year, in order to allow more time for preparation and testing of the instruments, after Mr. Dyson's return from the Eclipse Expedition to Sumatra. It was arranged with M. Lœwy, with the approval of the French Bureau des Longitudes, that the four portable transits belonging to the Royal Observatory, which had been used in previous longitude determinations from 1888 to 189S, and had been well tested, should be used by the two French and two English observers respectively, and after preliminary work with these instruments, both at Paris and Greenwich, the first stage of the longitude observations was commenced on March 17 and finished, as far as the English observers are concerned, on May 3. The observations were made in three groups of three, six, and three full nights (or their equivalents in half nights), the observers with their instruments being interchanged between the first and second, and again between the second and third groups. The English observers were Mr. Dyson and Mr. Hollis throughout, and the French M. Bigourdan and M. Rénan during the first group. Unfortunately at the end of this group M. Rénan was taken seriously ill, and it was necessary to replace him by another observer, M. Lancelin, and to recommence the work of the French observers, which is still in progress. It is proposed to carry out the second stage of the observations in the autumn. For these operations the Post Office authorities have courteously given the use of the telegraph line and the services of a telegraphist.
The Report here presented refers to the year from 1902 May 11 to 1903 May 10, and exhibits the state of the Observatory on the last-named day.
I. - Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:-
At Greenwich-
On loan-
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
II. - Astronomical Observations:-
Clocks and Chronographs. - For convenience in working the circuits required for registration of the seconds from the Sidereal Standard for the various instruments in different parts of the Observatory, a new distributing relay has been placed in the basement of the Altazimuth Pavilion which works four circuits, one of these being in connection with the relay in the Old Observatory building, which is used for local distribution to the instruments in that part of the Observatory.
Owing to the damage caused by rats gnawing the gutta-percha covering of the telegraphic wires in the Observatory and the consequent interruptions of the circuits, iron pipes have been laid down under the floors of the buildings, in which the wires are now carried.
The Sidereal Standard Clock, the clock "Dent 2017 " used with the Astrographic Equatorial, and" Graham 2" used in the Longitude Pavilion, have been cleaned and repaired during the year.
The transit-circle chronograph has also been cleaned and repaired, some parts which were worn considerably being replaced.
[Since the date of this report the Mean Solar Clock Dent 2012 was injured during a thunderstorm (May 17), the contact springs being broken and the platinum points fused. It is now being repaired. Several galvanometers in use for the time signal service were also destroyed.]
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-·
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 479, viz., 285 box chronometers, 41 pocket chronometers, and 153 deck-watches. In addition to these, 9 chronometers and 2 deck-watches are being tested after repair for the Indian Government.
In the year ending 1903 May 10 the average daily number of chronometers and deck-watches being rated was 571; the total number received was 1,337; the total number issued 1,288, and the number sent for repair 625. These include 22 box chronometers, 3 deck-watches and I pocket chronometer for the Indian Government. At the present time there are 12 box chronometers on trial for purchase for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 43° to 105°, 47 chronometers were sent in, 16 being rejected in the course of the trial on account of the difference between one week's rate and the next having exceeded 12 seconds. Out of the remaining 31 chronometers 18 were purchased for the Navy and 2 for the Transvaal Government. With the exception of the first 3 chronometers, the performance was decidedly below the average of
recent years, Thus the average trial number of the first 10 chronometers was 21.1, as against 17.1, 18.5, 17.9, and 16.6 in the previous four years, and the average for the first 20 was 26.3, as against 21.5 and 21.0 in the las t two years. As the trial numbers of several chronometers would be considerably reduced if a correction for progressive change of rate were made, it is not unlikely that the larger trial numbers found this year may be partly accounted for by the chronometers not being sufficiently seasoned.
For the annual trial of deck watches, lasting 16 weeks and including trials in the oven and in positions, 147 watches were entered, and of these 41 were purchased for the Navy. Among the watches sent for trial were 44 with centre seconds dials, of which 12 were purchased. There were 76 "Karrusel" watches in the trial, of which 20 were purchased. The performance of the deck-watches does not reach the high standard of last year, but fairly maintains the average of the previous seven years.
As the Admiralty desire to purchase a small number of pocket chronometers to gradually replace those at present in use on Surveying Vessels, pocket chronometers will be included in the annual trial of chronometers this year, and notice of this with a specification of the conditions has been issued to the makers. The next competitive trial of chronometers (box and pocket) will commence on July 4, and of deck-watches on October 24.
The Greenwich time-ball was not raised on two days during the year, owing to the violence of the wind. On May 13, through inadvertence, the ball was not raised at 13h; on September 14 the ball did not rest properly on the clips, and failed to remain up; on December 15 the ball dropped about 2 feet, when the check rope jammed between the piston and cylinder and prevented further drop; on ApriI4 the clips failed to release the piston; and on April 20 there was a failure in the electric connections. On these days the ball was raised again at 14h and dropped correctly.
The Greenwich time signal at 13h failed on April 20 owing to the interruption of the electric connections referred to above. The error of the time signal was inappreciable except on September 7 (Sunday), when it was 8.0s early, and October 7, when it was 0.7s early.
The automatic drop of the Deal time-ball failed on 6 days owing to interruptions of the telegraphic connections, and on April 20, when no signal went out from.
Greenwich. On 6 days the ball was not raised owing to the violence of the wind, On September 7 the ball was dropped 8s too soon owing to the error of the Greenwich signal, and on January 16 it was dropped 7s too soon (by a telegraph signal); it was raised again at 14h and dropped by hand.
The return signal from. Devonport failed on 38 days (of which 11 were Sundays) and could not be observed on 9 days owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0.2s on 88 per cent of the 316 days of observation, did not exceed 0.5s on 97 per cent., and never exceeded 1.0s.
The return signal from. the Portsmouth clock failed on 78 days (of which 41 were Sundays), and could not be observed on 5, days owing to interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0.2s on 85 per cent of the 280 day of observation, did not exceed 0.5s or 97 per cent., and never exceeded 1.0s.
The automatic signals from the Westminster clock have been received throughout the year except on 11 days, when the signal failed, and during the month of January while the clock was being repaired. The' apparent error of the clock was not greater than 0.5s on 21 per cent. of the days of observation, not greater than 1.0s on 39 per cent., not greater than 2.0s on 68 per cent., not greater than 3.0s on 90 per cent., not greater than 4.0s on 96 per cent., and exceeded 4s on 8 occasions. It is understood that the performance of the clock has been affected by bricklayers' work in the weight shaft in connection with electric lighting last October, and that the cleaning of the clock which was thus rendered necessary had to be deferred till the Parliamentary recess.
Longitude Operations. - The second stage of the re-determination of the Paris-Greenwich longitude was completed in the Autumn of 1902. As in the first stage carried out in the Spring and referred to in the last Report, observations were made simultaneously by two French and two English observers at adjacent stations. The observations of both the French and English observers were made in three groups of three, six, and three full nights (or their equivalents in half nights), the observers with their instruments being interchanged between the first and second and again between the second and third parts. In the determination made in the Autumn the stands were also interchanged with the instruments. The following table gives a summary of the number of nights of observation of the English observers, Mr. Dyson and Mr. Hollis:-
| Date. | Observer at | No. of nights on which signals were exchaged. |
No.of nights on which Clock Error was determined. |
||||
| Paris. | Greenwich. | Paris. | Greenwich. | Simultaneously. | |||
| 1902. | |||||||
| 1. March 17-30 | D. | H. | 13 | 5 | 9 | 4 | |
| II. April 6-24 | H. | D. | 19 | 10 | 11 | 6 | |
| III. April 27-May 3 | D. | H. | 7 | 3 | 5 | 3 | |
| I. Sept 21-26 | H. | D. | 6 | 4 | 6 | 4 | |
| II. Sept.29-Oct.22 | D. | H. | 24 | 11 | 13 | 8 | |
| III. Oct. 25-Nov.4 | H. | D. | 11 | 8 | 8 | 5 |
The reduction of the observations made by the English observers is completed with the exception of slight corrections which may have to be made in a very few instances to the assumed right ascensions of the stars.
The determination made in the Spring gave for the difference of longitude between Cassini's meridian and that of the Greenwich transit-circle 9m 20.974s, and for the difference of personal equation D - H = 0.041s. The determination made in the Autumn gave 9m 20.909s and the difference of personal equation D - H = 0.049s. In the first series, if the level determination had been based entirely on observations of the striding levels, the result would have been 9[m] 20.982s, and if entirely on the observations of nadirs 9m 20.969s. In the second Modes the difference between the results from "striding levels" and "nadirs" was only 0.002s. In the first series the probable error or the difference of longitude determined from one full night's observations was ± 0.04s and in the second series only ± 0..018s, giving for the probable error of the determination made in the Spring ± 0.0113s, and for that made in the Autumn ± 0.0047s. It is to be noted that in each series there was a double interchange of observers, so that the probable error includes any change of personal equation between the first and third parts, and this would appear to account to some extent for the larger probable error found for the first series.
The International Geodetic Association considering it desirable that a re-determination of the difference of longitude Potsdam-Greenwich should be made with their lately adopted Repsold registering micrometer, the longitude pavilion was placed at their disposal, and the Post Office authorities have given all the telegraphic facilities desired. Prof. Albrecht and Herr Obst installed their instruments in the last week in April, and the observations are now in progress.
Arrangements have been made for Major Burrard and Captain Lenox-Conyngham, of the Indian Survey, to swing" Von Sterneck" pendulums at the Royal Observatory soon after Visitation Day.
IX. - General Remarks:-
The work of the Observatory continues to grow in various directions, as is evidenced by this Report, and it is only through the zeal and energy with which the Assistants and Computers have worked that the pressure during the past year has been so well met. In particular, there has been a considerable development in the meridian work consequent on the adoption of an extensive programme of observation with the reflex zenith tube for determination of variation of latitude, a question of primary importance as affecting meridian observations. It is, however, in the photographic branch, under Mr. Hollis, that the pressure has been felt most severely in the past year, accentuated by the circumstance that the Paris longitude determination entailed much additional work, both for observations and reductions. …
The Report here presented refers to the year from 1903. May 11 to 1904 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:
At Greenwich-
On loan--
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and ArnoId 2, at the University Observatory, Oxford.
II.-Astronomical Observations:--
Clocks and Chronographs. - The transit-circle chronograph is now being repaired by Messrs. E. Dent & Co., some improvements, being made in the train of wheels. Since May 10, when the instrument was taken away, the registration of the transit-circle observations has been made on the chronograph of the Altazimuth.
The Mean Solar Clock (Dent 2012), injured during the thunderstorm of 1903 May 17, has been repaired. The electric clock Shepherd in the Ball Lobby has been thoroughly overhauled and new contact springs applied. The clock Mudge and Dutton, used in the chronometer room, has also been cleaned and repaired.
The sympathetic dials in the New Observatory gave considerable trouble in the latter part of 1903. They were sent to Messrs. E. Dent & Co. for alteration in January and have since their return performed satisfactorily.
VII.-Chronometers, Time Signals, Longitude Operations, &c.:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 513, viz., 299 box chronometers. 4z pocket chronometers, and 172 deck-watches. In addition to these, 13 chronometers are being tested after repair for the Indian Government.
In the year ending 1904 May 10J the average daily number of chronometers and deck-watches being rated was 609; the total number received was 1,377, the total number issued was 1,382, and the number sent for repair 584. These include 19
box chronometers, arid 2 deck-watches for the Indian Government. At the present time there are 4 eight-day box chronometers on trial for purchase for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 43° to 105°, 68 chronometers were sent in. During the trial 26 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 42 chronometers, 27 were purchased for the Navy, 3 for the Transvaal Government, and 8 for the Indian Government. There was a slight improvement in performance, 19 chronometers this year having trial numbers less than 30, as against 13 last year.
For the annual trial of deck-watches, lasting 16 weeks and including trials in the oven and in positions, 192 watches were entered, of which 114 were classified, and of these 42 were purchased for the Navy. Among the watches classified were 44 with centre seconds dials, of which 18. were purchased. There were 74 “Karrusel " watches classified, of which 29 were purchased. The performance of the deck-watches is very satisfactory, being above the average of the last nine years. There were 74 watches with, trial numbers less than, 80, as compared with 41 last year.
A competitive trial of pocket chronometers took place concurrently with the trial of box chronometers, and under the same conditions as regards length of trial and temperature, trials in positions as for deck-watches being included. Only 2 of the 9 pocket chronometers sent in came up to the standard for purchase.
The Greenwich time-ball was not raised on three days during the year, owing to the violence of the, wind. On January 24 the ball failed to drop although the clips were released. The ball was dropped 24s too soon on June 26, and on October 18, through a false signal, and about 30s too soon on September 13 (Sunday) through a mistake with the commutator.
The Greenwich time signal at 13h failed on May 18 through the effect of the thunderstorm on May 17. On May 31 (Sunday) it was I.0s late; on September 13 (Sunday) it was 30s early; on February 2 it was 0.8s late, through delay in the clock contact, and on May 8 (Sunday) it. as 1.0s early.
The automatic drop of the Deal time-ball failed on 18 days owing to interruptions of the telegraphic connections, and on May 18, when no signal left the Observatory. On 5 days the ball was not raised owing to the violence of the wind, On February 3 the ball was dropped 0.8s late owing to the error of the Greenwich signal. On the other days when the Greenwich signal was in error it apparently failed to reach Deal, and these days are included in the number 18. On July 11 the ball was dropped 6s late; it was raised again at 14h and dropped by hand.
The return signal from Devonport failed on 41 days (of which 8 were Sundays) and could not be observed on 9 days owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0.2s on 90 per cent. of the 313 days of observation, did not exceed 0.5s on 97 per cent., and never exceeded 1.0s
The return signal from Portsmouth failed on 99 days (of which 43 were Sundays) and could not be observed on 6 days owing to interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0.2s on 83 per cent. of the 258 days of observation, did not exceed 0.5s or 97 per cent., and never exceeded 1.0s.
The automatic signals from the Westminster clock have been received throughout the year except on 26 days, when the signal failed, and on 21 days it could not be observed. owing to interruptions from telegraphic signals. The apparent error of the clock was not greater than 0.5s on 19 per cent. of the days of observation, not greater than 1.0s on 43 per cent., not greater than 2.0s on 71 per cent., not greater than 3.0s on 93 per cent., not greater than 4.0s on 99 per cent., and exceeded 4.0s on two occasions.
Longitude Operations, &c. - The determination of the longitude of Potsdam by Prof. Albrecht and Dr. Wanach was completed in July. The result, which has been recently published by Prof. Albrecht, leads to an indirect determination of the longitude of Paris which is in close accordance with the results obtained by the Greenwich observers in 1902.
Major Burrard and Major Lenox-Conyngham, of the Indian Survey, swung their "Von Sterneck" pendulums in the Record room in July, and again in October, in order to standardise them before using them in India.
Staff-Commander Roberts, R.N., in charge of the chronometer depôt at Malta, attended at the Observatory during November and December to acquire practice in time-determination with a small transit instrument.
It may here be mentioned that an exhibit of photographs illustrating the work of the Royal Observatory has been prepared for the St. Louis Exhibition, and was sent off early in January.
IX.-General Remarks:-
The work of the chronometer branch continues to develop with the growth of the Navy, and strenuous efforts on the part of the staff concerned are required to deal with the continuous increase of work in this branch.
The Report here presented refers to the year from 1904 May 11 to 1905 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:-
At Greenwich-
On loan -
Clocks. - Dent No. 1916, and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and ArnoId 2, at the University Observatory, Oxford.
II. -Astronomical Observations:-
Clocks and Chronographs. - The transit-circle chronograph has been repaired by Messrs. E. Dent & Co., and some improvements have been made in the train of wheels. A platform and guiding cheeks have also been introduced to guard against jerks when the barrel is being put in the chronograph.
The contact pallets of the Mean Solar Clock (Dent 2012) have been repaired.
The Clock Hardy, which was much rusted owing to damp weather, has been cleaned by Messrs. Kullberg, who have made alterations in the case to protect the clock from damp as far as possible.
VII.-Chronometers, Time Signals, and Miscellaneous:-
The number of Government marine chronometers and deck-watches now being tested at the Observatory is 571. viz., 399 box chronometers, 42 pocket chronometers, and 130 deck-watches.
In the year ending 1905 May 10, the average daily number of chronometers and deck-watches being rated was 686; the total number received was 1,734, the total number issued was 1,691, and the number sent for repair 735. These include 32 box chronometers, 2 pocket chronometers, and 3 deck-watches for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 41° to 104°, 67 chronometers were sent in. During the trial 24 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 43 chronometers, 10 were purchased for the Navy, and 9 for the Indian Government. The performance was about the same as in recent years, 16 chronometers having trial numbers less than 30, as against 19 last ~'ear and 13 the year before.
A competitive trial of pocket chronometers took place concurrently with the trial of box chronometers, and under the same conditions as regards length of trial and temperature, trials in positions as for deck-watches being included. Only 1 of the 11 pocket chronometers sent in came up to the standard for purchase.
For the annual trial of deck-watches, lasting 16 weeks and including trials in the oven and in positions, 224 watches were entered, of which 128 were classified, and of these 19 were purchased for the Navy. Among the watches classified were 44 with centre-seconds dials, of which 7 were purchased. There were 76 “Karrusel" or "Tourbillon" watches classified, of which 13 were purchased. The performance of the deck-watches is very satisfactory, and shows a marked improvement on that of any previous year.
It is noteworthy that the performance of the watches compares well with that of the box chronometers in this year's trial, as tested by the trial numbers a + 2b, though it is to be remarked that the chronometer trial is rather more severe, the temperature having been from 41.2° to 104.0° for the chronometers and 41.6° to 90.7° for the watches. The following is a comparison of the trial a + 2b (omitting the part due to tests in position for the watches) for the chronometers and deck watches, respectively, in the trials 1904-5, the watches having been re-arranged for this comparison in order of a + 2b:-
| Average Trial Numbers a + 2b. | |||||||
| Nos. | 1-5 | 6-10 | 11-15 | 16-20 | 21-25 | 26-30 | |
| Chronometers | 16.8 | 21.3 | 24.9 | 30.8 | 33.7 | 35.2 | |
| Deck-watches | 17.6 | 24.8 | 29.3 | 33.1 | 35.2 | 37.0 | |
It may be added that the values of the trial numbers a + 2b for the watches standing respectively first and fourth are actually smaller than those standing respectively first and second in the chronometer trial.
The next trial of watches will commence on August 5.
The Greenwich time-ball was not raised on five days during the year, owing to the violence of the wind. On all other days it was dropped correctly.
The Greenwich time signal at 13h was 0.4s late on three days (all Sundays), May 23 , June 19, and December 18. On all other days the error of the signal was less than this.
The automatic drop of the Deal time-ball failed on 8 days owing to interruptions telegraphic communications. On 5 days the ball was not raised owing to the violence of the wind, On February 16 the ball was dropped 12.5s early owing to a false signal on the line just before the Greenwich signal.
The return signal from Devonport failed on 35 days (of which 9 were Sundays), and could not be observed on 10 days owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not 0.2s on 90 per cent. of the 319 days of observation, and did not exceed 0.5s on 97 per cent. On 9 occasions it exceeded 0.5s, but never exceeded 1.0s. The average error for the year was ± 0.10s.
The return signal from Portsmouth failed on 65 days (of which 42 were Sundays), and could not be observed on 14 days owing to the interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock did not exceed 0.2s on 84 per cent. of the 285 days of observation, did not exceed 0.5s on 97 per cent., and exceeded 1.0s on two occasions. The average error for the year was ± 0.17s.
The automatic signals from the Westminster clock have been received much more regularly during this year. On 6 days the signal failed, and on 4 other days it was interrupted by telegraph signals. An improvement is also shown in the performance of the clock. Its apparent error was not greater than 0.5s on 33 per cent. of the days of observation, not greater than 18'0 on 58 per cent., not greater than 2"'0 on 87 per cent., not greater than 1.0s on 98 per cent., and exceeded 3.0s on only 4 occasions.
Provision has been made in the Navy Estimates for the observation of the total Solar Eclipse of 1905 August 30 by a party of three observers on the coast of Tunis, where the weather conditions are promising. It is proposed to take photographs of the corona for detail and extension with the Thompson 9 in. coronagraph, the 13 in. astrographic refractor, and the 4 in. Dallmeyer rapid rectilinear lens, and also photographs of the spectrum with the two spectroscopes lent by Major Hills, R.E., as in 1900 and 1901.
On the invitation of the Canadian Government, Mr. Maunder is joining their expedition to Labrador to observe the eclipse at the other end of the track, taking the Dallmeyer 4 in. coronagraph and a 4 in. rapid rectilinear lens for photographs of the corona, as in Mauritius in 1901.
The Report here presented refers to the year from 1905 May 11 to 1906 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
A permanent storehouse for portable instruments, huts, chronometer baskets, and general stores, is much needed to take the place of the existing wooden sheds, which have various· disadvantages, the most serious being the risk of fire. A suitable site for this could be found on the south-west side of the New Observatory, where the slope of the ground gives facilities for the erection, at comparatively small cost, of a partly sunk basement, which would not interfere in any way with the New Observatory building.
The principal movable instruments are thus distributed:-
On loan-
Clocks.-Dent No. 1916 and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
One Hilger Chronograph lent to Prof. Karl Pearson at University College, London.
II.-Astronomical Observations:-
Clocks and Chronographs.- As the altazimuth chronograph was not going satisfactorily, being liable to large changes of rate, the springs which controlled the friction governor were removed so as to make its action depend on gravity alone. After this change its going was found to be much, more uniform. There still remains an inequality with a period of 16 minutes (the same as that of the driving barrel), but this is of no practical importance.
VII.-Chronometers, Time Signals, and Miscellaneous:--
The number of Government marine chronometers and watches now at the Observatory is 584, viz., 393 box chronometers, 48 pocket chronometers, and 90 chronometer watches, and 53 hack watches. In addition to these there are at the Observatory, 21 hack watches on trial for purchase and 10 box chronometers belonging to the Indian Government.
In the year ending 1906 May 10, the average daily number of chronometers and watches being rated was 736, the total number received was 1,525, the total number issued was 1,478, and the number sent for repair 658. These include 27 box chronometers, 1 pocket chronometer, and 1 deck-watch for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks, with a range of temperature from 44° to 104°, 59 chronometers were sent in. During the trial 33 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 26 chronometers, 6 were purchased for the Navy and 6 for the Indian Government. The performance of the chronometers shows a decided falling off as compared with previous years, from 1894 onwards. The number of chronometers rejected in the course of the trial is larger than in any previous year, though the number sent in was smaller, than usual, and the number classified as not having exceeded the limit of 12 seconds for b is the smallest in any trial of recent years.
A competitive trial of pocket chronometers took place concurrently with the trial of box chronometers, and under the same conditions as regards length of trial and temperature trials in positions as for chronometer watches being included. Only 2 of the 14 pocket chronometers sent in came up to the standard for purchase; but these showed a marked improvement on the best in last year's trial.
For the annual trial of chronometer watches, lasting 16 weeks and including trials in the oven and in positions, 221 watches were entered, of which 123 were classified, and of these 30 were purchased for the Navy. Among the watches classified were 44 with centre seconds dials, or which 9 were purchased. There were 77 "Karrusel" or "'Tourbillon" watches classified, of which 21 were purchased. The performance of the watches is very satisfactory, and compares well with that of the box chronometers. Taking the trial number a + 2b as a criterion the first 30 watches may be considered as coming up to the standard for a marine chronometer. The trial number a + 2b for the first watch this year, is equal to that for the first watch last year, both being markedly superior to that for the first box chronometer this year.
The next trial of watches will commence on August 4.
The Greenwich time-ball was not raised on one day, owing to the violence of the wind. On December 7 it dropped from the cross correctly, but was jammed by the check rope when about half way down. A new cover to the cylinder to prevent water entering has been so arranged as to guard against such accidents in the future.
The Greenwich time signal at 13h was 1s.0 early on one day. On all other days the error of the signal was a small fraction of a second.
The automatic drop of the Deal time-ball failed on 5 days owing to interruptions of the telegraphic communications. There was no day on which the ball was not raised owing to the violence of the wind. On January 9 the ball was dropped 17s .0 early owing to a false signal on the line just before the Greenwich signal. On June 19 the current failed to drop the ball.
The return signal from Devonport failed on 24 days (of which 10 were Sundays), and could not be observed on 12 days owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0s.2 on 92 per cent. of the 326 days of observation, and did notexceed 0s·5 on 97 per cent. On 8 occasions it exceeded 0s.5, and on one exceeded 1s.0. The average error for the year was ±0s.08.
The return signal from Portsmouth failed on 41 days (of which 23 were Sundays), and could not be observed on 10 days owing to interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 74 per cent. of the 311 days of observation, did not exceed 0s.5 on 97 per cent., and never exceeded 1s.0. The average error for the year was ±0s.17.
The automatic signals from the Westminster clock have been received regularly during the year. On 14 days the signal failed, and on 3 other days it was interrupted by telegraph signals. The improvement in the performance of the clock reported last year has been fully maintained. Its apparent error was not greater than 0s.5 on 31 per cent. of the days of observation, not greater than 1s.0 on 64 per cent., not greater than 2s.0 on 96 per cent., not greater than 3s.0 on 99 per cent., and exceeded 3s.0 on only two occasions.
Messrs. E. Dent & Co. report that the Westminster clock stopped at 9h 20m p.m. on March 13 owing to a plank having been inadvertently left behind the dial in such a position that it fouled the internal counterpoise of the hand as it travelled round. The clock was started going again a little after 9h on the following morning.
The insulated wires for the clock and observing circuits leading, in an underground pipe, from the Transit Circle room to the Altazimuth Pavilion and the sidereal standard clock in the Magnet Basement had, for some time past, given trouble through their defective state, and last August an entirely new set of wires, carried above~ ground where practicable, was provided by the Post Office authorities. Ample provision has now been made in these circuits to meet all our requirements.
VIII.-Personal Establishment:-
Mr. Lewis has charge of the clocks, time signals, and chronometers, and of the 28-inch equatorial. Mr. Bowyer, Mr. Edney, and Mr. Furner assist Mr. Lewis, Mr. Bryant, and Mr. Crommelin respectively.
The Report here presented refers to the year from 1906 May 11 to 1907 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
A new porch and covered glass passage have been erected in front of the Astronomer Royal's official residence in substitution for the old porch and passage which required renewal, and a new and wider pathway has been laid in granolithic cement in front, leading from the Old Observatory building to the Chronograph room.
The cross-trees of the Time Ball mast have been renewed.
The lightning conductors from the Octagon room roof and from the Magnetic Pavilion have been connected to distant water mains, so that there would in the former case be no risk of interference with the earth connections of the time-signal and other telegraph circuits of the Observatory.
Provision has been made in the Navy Estimates for the permanent storehouse for portable instruments, huts, chronometer baskets, &c., referred to in the last Report, and plans for the building have been prepared.
The principal movable instruments are thus distributed:--
On loan-
Clocks.-Dent No. 1916 and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory j Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
II.-Astronomical Observations:-
Clocks and Chronographs.- The clock Dent 2, fitted with a mercurial pendulum, has been thoroughly overhauled, the contact springs improved, and a new contact spring for a minute signal added. The clock is intended to be used when the Sidereal Standard is under repair. Dent 2009, in the S.E. Dome, has been cleaned, and Graham 1, in the Altazimuth Dome, is now being cleaned by E. Dent & Co.
VII.-Chronometers, Time Signals, and Miscellaneous:--
The number of Government marine chronometers and watches now at the Observatory is 510, viz., 347 box chronometers, 20 pocket chronometers, 76 chronometer watches, and 67 hack watches. In addition to these there are, at the Observatory, 18 hack watches and 10 chronometer watches on trial for purchase, and 5 box chronometers belonging to the Indian Government.
In the year ending 1907 May 10, the average daily number of chronometers and watches being rated was 656, the total number received was 1,351, the total number issued was 1,420, and the number sent for repair 548. These include 27 box chronometers, 1 pocket chronometer, and 3 deck-watches for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks with a range of temperature from 42° to 106°, 46 chronometers were sent in. During the, trial 21 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 25 chronometers, 6 were purchased for the Navy and 7 for the Indian Government. The performance of the chronometers generally is hardly up to the high average of recent years, but a good proportion fully come up to the standard for the Royal Navy.
A competitive trial of pocket chronometers took place concurrently with the trial of box chronometers, and under the same conditions as regards length of trial and temperature-trials in position as for chronometer watches being included. None of the 14 pocket chronometers sent in came up to the standard for purchase.
For the annual trial of chronometer watches, lasting 16 weeks and including trials in the oven and in positions, 179 watches were entered, of which 102 were classified, and of these 16 were purchased for the Navy. Among the watches classified were 27 with centre seconds dials, of which 6 were purchased. There were 61 " Karrusel " or "Tourbillon" watches classified, of which 8 were purchased.
'The performance of the watches is not quite' so good as for the last two years, but there are a good number which may be fairly classed ,as chronometer watches.
The next trial of chronometers will commence on June 15, and of chronometer watches on August 3.
The Greenwich time-ball was not raised on one day, owing to the violence of the wind. On November 14 the clips failed to hold the ball, which fell about two minutes early. It was raised again and dropped correctly.
On February 8 the Greenwich clock (Dent 2012) closed the circuit 2s late, and on March 12 the clock was 1s fast. On these days the signals were wrong, and the ball also was not dropped correctly at l3h. It was raised again and dropped correctly at 14h.
The automatic drop of the Deal time-ball failed on 7 days owing to interruptions of the telegraphic communications; but on 3 of these occasions the attendant, being warned, dropped the ball correctly by hand. On 3 days, the ball was not raised owing to the violence of the wind. On October 16 the current was too weak to drop the ball.
The return signal from Devonport failed on 40 days (of which 9 were Sundays), and could not be observed on 6 days owing to interruptions by telegraph signals.
The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0s.02 on 89 per cent. of the 318 days of observation and did not exceed 0s.5 on 97 per cent. On 10 occasions it exceeded 0s.5, but never exceeded 1s.0. The average error for the year was ±0s.12.
The return signal from Portsmouth failed on 40 days (of which 26 were Sundays), and could not be observed on 6 days owing to interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 80 per cent. of the 319 days of observation, did not exceed 0s.5 on 98 per cent., and exceeded 1s.0 on one day. The average error for the year was ±0s.18.
The automatic signals from the Westminster clock have been received regularly during the year ending May 10. On 4 days the signal failed, and on 9 other days it was interrupted by telegraph signals. The improvement in the performance of the clock reported last year has been fully maintained. Its apparent error was not greater than 0s.5 on 39 per cent. of the days of observation, not greater than 1s.0 on 67 per cent., not greater than 2s.0 on 93 per cent., not greater than 3s.0 on 99 per cent., and exceeded 3s.0 on only two occasions.
At the request of the Hydrographer, Lieutenant F. C. Hanning-Lee, R.N., attended the Observatory from October 17 to December 14 for a course of instruction in the use of the portable transit instrument for time determination and in the work of the chronometer branch before taking up his appointment as Superintendent of the chronometer depot at Malta.
VIII.-Personal Establishment:-
Mr. Lewis has charge of the clocks, time signals,and chronometers, and of the 28-inch equatorial. … Mr. Bowyer, Mr. Cullen, Mr. Edney, and Mr. Furner assist Mr. Lewis, Mr. Thackeray, Mr. Bryant, and Mr. Crommelin respectively.
The Report here presented refers to the year from 1907 May 11 to 1908 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
The building of the new Storehouse for portable instruments, chronometer baskets and general stores, referred to in the last two Reports, was commenced at the. end of January and having been pushed on rapidly is now practically completed.
The principal movable instruments are thus distributed:-
On loan-
Clocks.-Dent No. 1916 and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; and Arnold 2, at the University Observatory, Oxford.
II.-Astronomical Observations:-
Clocks and Chronographs.- The Sidereal Stan9-ard clock was taken away by E. Dent & Co. for repair on July 16, and was returned on July 22.
VII.-Chronometers, Time Signals, and Miscellaneous:-
The number of Government marine chronometers and watches now at the Observatory is 389, viz., 255 box chronometers, 23 pocket chronometers, 68 chronometer watches, and 43 hack watches. In addition to these there are, at the Observatory, 27 hack watches on trial for purchase, and also 8 box chronometers and 2 watches belonging to the Indian Government.
In the year ending 1908 May 10, the average daily number of chronometers and watches being rated was 589, the total number received was 1;298, the total number issued was 1,415, and the number sent for repair 575. These include 11 box chronometers, and 2 deck-watches for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks with a range of temperature from 45° to 106°, 28 chronometers were sent in. During the trial 13 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 15 chronometers, 9 were purchased for the Navy and 6 for the Indian Government. There is a serious falling off in the performance of the chronometers as well as in the number submitted for trial.
A competitive trial of pocket chronometers took place concurrently with the trial of box chronometers, and under the same conditions as regards length of trial and temperature-trials in position as for chronometer watches being included. Of the 8 pocket chronometers sent in, 3 were purchased for the Navy.
For the annual trial of chronometer watches, lasting 16 weeks and including trials in the oven and in positions, 156 watches were entered, of which 43 were classified, and of these 32 were purchased for the Navy. Among the watches classified were 10 with centre seconds dials, of which 8 were purchased. There were 17. " Karrusel " or " Tourbillon " watches classified, of which 15 were purchased. The performance of the watches this. year shows an improvement on that of last year and fairly comes up to the average of previous years.
It has been arranged that in future pocket chronometers and chronometer watches shall be tested together under the same conditions for the trial.
The next trial of box chronometers will commence on June 20, and of pocket chronometers and chronometer watches on August 1.
The Greenwich time-ball was not raised on one day (December 14), owing to the violence of the wind. On June 6 the clips failed to hold the ball, which fell about two minutes too early. It was raised again and dropped correctly.
On December 3 the Greenwich Mean Solar clock (Dent 2012) gave a false signal 30s before the hour, which dropped the Greenwich time-ball. It was raised again and dropped at 14h. The 13h signal left the Observatory correctly.
The automatic drop of the Deal time-ball failed on 6 days owing to interruptions of the telegraphic communications. On 1 day the ball was not raised owing to the violence of the wind. On 10 days the current was too weak to drop the ball; but on 3 of these occasions the attendant dropped the ball correctly by hand. On July 3, through inadvertence, the apparatus at Deal was not set correctly, and the ball did not drop.
The return signal from Devonport failed on 61 days (of which 9 were Sundays), and could not be observed on 31 days (of which 15 were Sundays) owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0s.2 on 88 per cent. of the 273 days of observation, and did not exceed 0s.5 on 96 per cent. On 12 occasions it exceeded 0s.5, but never exceeded 1s.0. The average error for the year was ±0s.14.
The return signal from Portsmouth failed on 50 days (of which 26 were Sundays), and could not be observed on 21 days (of which 15 were Sundays) owing to interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 75 per cent. Of the 295 days of observation, did not exceed 0s.5 on 98 per cent., and was between 0s.5 and 1s.0 on 6 days. The average error for the year was ±0s.18.
Return signals from Portland have been received regularly from 1907 May 29. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 70 per cent. of the 216 days of observation, did not exceed 0s.5 on 90 per cent., and exceeded 0s.5 on 21 days, being over one second on three of these. The average error for the period was ± 0s.23.
The automatic signals from the Westminster clock have been received regularly since June 6, previous to which date the clock was under repair. On 8 days the signal failed, and on one day it was interrupted by telegraph signals. Its apparent error was not greater than 0s.5 on 32 per cent. of the days of observation, not greater than 1s.0 on 63 per cent., not greater than 2s.0 on 93 per cent., not greater than 3s.0 on 99 per cent., and exceeded 3s.0 on only two occasions. Owing to an accumulation of snow on the hands, the clock stopped at 5h 50m a.m. on 1908 January 8. It was re-started at noon.
In connection with a telegraphic determination of the longitude of Ascension, referred both to Greenwich and the Cape Observatories, which the Hydrographer had arranged to undertake, Captain Monro, R.N., and, Lieutenant Gibson, R.N., were attached to the Observatory from September 16 to October 14 to practise observations with a portable transit under the guidance of Mr. Hollis and Mr. Harold Christie, and to obtain determinations of their personal equations referred to the Standard Observer with the Transit-Circle. Mr. R. T. Pett, of the Cape Observatory, who was on leave in England at that time, was also attached to the Observatory from September 16 to October 4 for the determination of his personal equation with the Transit-Circle so as to connect the Standard Observers at Greenwich and the Cape in view of the proposed longitude determination Greenwich-Ascension-Cape, which connects the Cape and Greenwich indirectly through Ascension. A further determination of personal equation will be made by Captain Monro on his return to England in July after the longitude operations.
The Eastern Telegraph Company kindly gave the free use of their cable from Porthcurno to the Cape viâ Ascension on Saturday and Sunday nights during February, and Mr. Judd, Electrician-in-Chief of the Company, with his staff gave every assistance in making arrangements for signalling through the great length of cable from Porthcurno to Ascension, 4,211 nautical miles, without a relay. Preliminary experiments with an artificial cable at the Eastern Telegraph Company's London office were made on September 27 and October 9, and it was found that by making special arrangements satisfactory signals could be obtained through this length of cable with a syphon recorder.
By arrangement with the Hydrographer, Captain Simpson, R.N., took charge of the work in connection with the transmission of signals between Greenwich and Ascension viâ Porthcurno during February, exchanges of signals being made on seven nights during the month. The accordance of the times of transmission between Porthcurno and Ascension is very satisfactory, showing that the signals recorded through this great length of cable can be read off with considerable accuracy, and the individual results for longitude on the separate nights also accord well.
It is proposed to undertake this year a telegraphic determination of the longitude of Malta, for which provision has been made in the Navy Estimates.
VIII.-Personal Establishment:
Mr. Lewis has charge of the clocks, time signals, and chronometers, and of the 28-inch equatorial. … Mr. Bowyer, Mr. Cullen, Mr. Edney, and Mr. Furner assist Mr. Lewis, Mr. Thackeray, Mr. Bryant, and Mr. Crommelin respectively.
The Report here presented refers to the year from 1908 May 11 to 1909 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:-
On loan-
Clocks.-Dent No. 1916 and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; Arnold 2, at the University Observatory, Oxford; and Graham 2, at Malta temporarily for Longitude Observations.
One Hilger Chronograph at Malta temporarily.
Transit C was taken out to Malta for use in connection with the first part of the Longitude Observations and was brought back again. Transit B is now at Malta for the second part of the Observations, together with an Observing Hut, the Clock Graham 2 and one Hilger Chronograph.
A collection of historical and modern astronomical and meteorological instruments, models, chronometers, photographs, and diagrams representative of the work of the Royal Observatory was sent to the Franco-British Exhibition on 1908, May 25. The exhibits were returned on November 11.
II.-Astronomical Observations:-
Clocks and Chronographs.- The clock Graham 2 was taken from the Thompson Dome and sent to Messrs. E. Dent & Co. for repair previous to being used in the determination of the longitude of Malta. It was sent to Malta on February 5. Arnold 1 was set up in the Dome to replace Graham 2.
VII.-Chronometers, Time Signals, and Miscellaneous:--
The number of Government marine chronometers and watches now at the Observatory is 407, viz., 242 box chronometers, 27 pocket chronometers, 81 chronometer watches, and 57 hack watches. In addition to these there are, at the Observatory, 9 hack watches and 2 high-class stop watches on trial for purchase, and also 25 box chronometers belonging to the Indian Government.
In the year ending 1909 May 10, the average daily number of chronometers and watches being rated was 520, the total number received was 1,565, the total number issued was 1,548, and the number sent for repair 678. These include 36 box chronometers and 2 pocket chronometers for the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks with a range of temperature from 41° to 104°, 48 chronometers were sent in. During the trial 15 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 33 chronometers, 9 were purchased for the Navy and 4 for the Indian Government.
The performance of the chronometers generally came up to the standard attained previous to last year, when there was such a serious falling off both in numbers sent in and in performance.
For the annual trial of chronometer watches, lasting 16 weeks and including trials in the oven and in positions, 157 watches were entered, of which 66 were classified, and of these 51 were purchased for the Navy. Among the watches classified were 13 with centre-seconds dials; of these 10 were purchased. There were 28 "Karrusel" or "Tourbillon" watches classified, of which 20 were purchased. The performance of the watches this year shows an improvement on that of last year.
A trial of pocket chronometers took place concurrent.ly with the trial of chronometer watches, and under the same conditions as regards duration of trial, temperatures, and positions. Of the 11 pocket chronometers sent in, 2 were purchased for the Navy.
The next trial of box chronometers will commence on June 19, and of pocket chronometers and chronometer watches on July 31.
The Greenwich time-ball was not raised on one day (April 30), owing to the violence of the wind. On two days, March 19 and April 16, in consequence of the clips not being set, the ball was not held in position for dropping at 13h. On each occasion the ball was raised at 14h and dropped correctly. On June 11 the train of the Mean Solar clock stopped for 2s just before 13h , and the ball was dropped 2s late. The I3h signal was also 2s late on this day.
On the morning of January 7 it was found on working up transits of stars obtained after a week of cloudy weather, that the adopted error of the Sidereal Standard clock found by carrying on: its rate from December 31, and checked by comparisons with the other Observatory clocks, and also with 19 of the best chronometers in the Annual Trial, was erroneous to the amount of fully 2 seconds. The time signals for the period January 1 to 6 are therefore to some extent erroneous, and consequently in taking percentage" and averages for the errors of the Devonport, Portsmouth, Portland, and Westminster clocks, the signals from January 1 to 7 have been omitted, as being affected with the uncertain error of the Greenwich clock.
The automatic drop of the Deal time-ball failed on 5 days owing to interruptions of the telegraphic communications. On 2 days the ball was not raised owing to the violence of the wind. On 2 days the current was too weak to drop the ball. On 1 day, June 29, a false current dropped the ball 12s too soon.
The return signal from Devonport failed on 59 days (of which 11 were Sundays), and could not be observed on 28 days (of which 22 were Sundays) owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0s.2 on 85 per cent. of the 272 days of observation, and did not exceed 0s.5 on 97 per cent. On 8 occasions it exceeded 0s.5, but never exceeded 1s.0. The average error for the year was ±0s.13.
The return signal from Portsmouth failed on 40 days (of which 22 were Sundays), and could not be observed on 33 days (of which 24 were Sundays) owing to interruption by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 75 per cent. of the 286 days of observation, did not exceed 0s.5 on 97 per cent., was between 0s.5 and 1s.0 on 4 days, and exceeded 1s.0 on 4 days. The average error for the year was ±0s.20.
The return signal from Portland failed on 57 days (of which 30 were Sundays), and could not be observed on 26 days (of which 22 were Sundays), owing to interruptions by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 89 per cent. Of the 277 days of observation, did not exceed 0s.5 on 97 per cent., exceeded 0s.5 on 9 days, on one of which it was over 1s.0. The average error for the year was ± 0s.14.
Tho automatic signals from the Westminster clock have been received regularly since the last report. On 1 day the signal failed, and on 8 days it was interrupted by telegraph signals. Its apparent error was not greater than 0s.5 on 49 per cent. of the days of observation, not greater than 1s.0 on 76 per cent., not greater than 2s.0 on 96 per cent., not greater than 3s.0 on 99 per cent., and never exceeded 4s.0.
A telegraphic determination of the longitude of Malta was undertaken in the spring; the observations had not been quite completed at the date of this Report. The electrical arrangements were generally similar to those used in the determination of the longitude of Ascension last year, and the signals were transmitted directly between Porthcurnow and Malta without a relay. The Eastern Telegraph Company again kindly gave the free use of a cable for the exchanges of signals. At Malta the pier and observing hut were erected on the roof of the Eastern Telegraph Company's offices at St. George's Bay.
The observations were made by Mr. Eddington and Mr. Harold Christie; they were divided into two parts, the observers with their instruments being interchanged in the interval. The observations of the first part were made from February 20 to March 8. The second part was not started until May 8, being greatly delayed by an interruption of the cable; it was finished on May 16. Exchanges of signals were made on 10 nights in the first part, and on 8 nights in the second part.
Captain O. E. Monro, R.N., and Lieutenant Gibson, R.N., of H.M.S. "Mutine," were attached to the Observatory from, July 15 to August 18 for the purpose of reducing the observations made for determining the longitude, Greenwich-Ascension-Cape. Captain Monro returned on September 9 to write his report, and the result, which is subject to some small corrections, was communicated to the Royal Astronomical Society in November.
VIII.-Personal Establishment:-
| Branch | Assistants | Established Computers | Supermumerary Computers | |
| Time Signals, Chronometers, and 28-inch Refractor. |
Lewis | Bowyer | *Witney, *Green, *Shepperd. |
* Qualified as Observers with one or more of the instruments.
… The Time Signal .System was introduced in 1854 without any addition to the Staff, and this has since greatly developed and become a source of considerable revenue to the Post Office. At that time Sir G. B. Airy said:- "I am impressed with the feeling that the strength of our Establishment is now loaded to the utmost that it can bear. A brief review of the progress of the science of Astronomy and of the arts related to it will show that this must be expected." …
The Report here presented refers to the year from 1909 May 11 to 1910 May 10, and exhibits the state of the Observatory on the last-named day.
I.-Buildings and Grounds, Movable Property, and Library:-
The principal movable instruments are thus distributed:-
On loan-
Clocks.-Dent No. 1916 and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory j Dent No. 2010, at Devonport; Arnold 2, at the University Observatory, Oxford.
II.-Astronomical Observations:-
Clocks and Chronographs.- The clock Graham 2, after use in, the Malta Iongitude determination; was sent to Messrs. E. Dent & Co. for testing and, cleaning. The clock Dent 2017 is at present with the same firm for cleaning and testing.
VII.-Chronometers, Time Signals, and Longitude Operations:-
The number of Government marine chronometers and watches now at the Observatory is 455, viz., 232 box chronometers, 30 pocket chronometers, 108 chronometer watches, and 85 hack watches.
In addition to these there are, at the Observatory, 17 eight-day chronometers on trial for purchase for the Indian Government, and 5 box chronometers being tested after repair. Also one chronograph watch awaiting repair.
The are also 19 hack watches on trial for purchase by the Admiralty. In the year ending 1910 May 10, the average daily number of chronometers and watches being rated was 596, the total number received was 1,746, the total number issued was 1,684, and the number sent for repair 776. This last number includes 53 box chronometers and 1 pocket chronometer belonging to the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks with a range of temperature from 46° to 106°, 66 chronometers were sent in. During the trial 24 were rejected because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 42 chronometers, 8 were purchased for the Navy and 4 for the Indian Government.
The performance of the chronometers generally was very satisfactory.
For the annual trial of chronometer watches, lasting 16 weeks and including trials in the oven and in positions, 173 watches were entered, of which 74 were classified, and of these 35 were purchased for the Navy. Among the watches classified were 22 with centre-seconds' dials; of these 9 were purchased. There were 16 "Karrusel" or "Tourbillon" watches classified, of which 8 were purchased. The performance of the watches, on the whole, is as good as that of last year.
A trial of pocket chronometers took place concurrently with the trial of chronometer watches, and under the same conditions as regards duration of trial, temperatures, and positions. Of the 17 pocket chronometers sent in, 2 were purchased for the Navy.
The next trial of box chronometers will commence on June 18, and of pocket chronometers and chronometer watches on July 30.
Provision has been made to receive a number of non-magnetic watches on trial. These will be tested concurrently and under the same conditions as the chronometer watches.
The Greenwich time-ball was not raised on one day (February 17), owing to the violence of the wind. On May 8 (Sunday), in consequence of the clips not being set, the ball was not held in position for dropping at 13h.
During the cloudy weather at the end of October, an incorrect clock rate was carried on, which caused an error in the signals on November 1 and November 2, the signals being 1"' 0 early on the first date and 1"' 4 early on the latter date.
The automatic drop of the Deal time-ball failed on 3 days owing to interruptions of the telegraphic communications. On April 6, the current was too weak to drop the ball. On February 24 a false signal dropped the ball 8 seconds too soon. Return signals have been received daily except on 37 days.
The return signal from Devonport failed on 65 days (of which 10 were Sundays), and could not be observed on 38 days (of which 21 were Sundays) owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0s.2 on 90 per cent. of the 260 days of observation, and did not exceed 0s.5 on 97 per cent. On 7 occasions it exceeded 0s.5, but never exceeded 1s.0. The average error for the year was ±0s.11.
The return signal from Portsmouth failed on 41 days (of which 21 were Sundays), and could not be observed on 31 days (of which 24 were Sundays) owing to interruptions by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 67 per cent. of the 291 days of observation, and did not exceed 0s.5 on 97 per cent. On 10 occasions it exceeded 0s.5, but never exceeded 1s.0. The average error for the year was ±0s.19.
The return signal from Portland failed on 63 days (of which 25 were Sundays), and could not be observed on 32 days (of which 24 were Sundays), owing to interruptions by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 91 per cent. Of the 268 days of observation, did not exceed 0s.5 on 98 per cent., exceeded 0s.5 on 6 occasions, on two of which it was over 18 '0. The average error for the year was ± 0s.12.
The automatic signals from the Westminster clock have been received regularly since the last report. On 11 days the signal failed, and on 2 days it was interrupted by telegraph signals. Its apparent error was not greater than 0s.5 on 41 per cent. of the days of observation, not greater than 1s.0 on 77 per cent., not greater than 2s.0 on 98 per cent., and was between 2 and 3" on six occasions, but never exceeded 3s.
The reduction of the observations for the determination of the longitude of Malta has been completed, but the final result cannot be given until the observing station at Malta has been accurately connected by triangulation with Spencer's monument, which is the fundamental point adopted. Using, however, the difference of longitude between these. points, measured as accurately as possible, on the War Office charts, the longitude of Spencer's monument (old site) is 0h 58m 2s. 595 ± 0s.010 E. This is in close agreement with the determination by Auwers and Gill “German Transit of Venus Expedition, 1875,” viz., 0h 58m 2s.65 E.
At the request of the Secretary of the Admiralty, Lieutenant Harold F. J. Young, R.N., was attached to the Observatory from October 4 to November 16 for practice in the use of a small transit instrument preparatory to taking up his appointment as Superintendent of the Chart and Chronometer Depot at Malta.
VIII.-Personal Establishment:
| Branch | Assistants | Established Computers | Supermumerary Computers | |
| Time Signals, Chronometers, and 28-inch Refractor. |
Lewis | Bowyer | *Shepperd, *Green, Newton. |
* Qualified as Observers with one or more of the instruments.
IX.-General Remarks:-
The large increase of work in the Chronometer and Time Signal branch may be inferred from the number of Navy chronometers rated daily at the Observatory, which increased from 194 in 1880-81 to 596, in 1909-10.
The Report here presented refers to the year '£rom 1910 May 11 to 1911 May 10, and exhibits the state of the Observatory on the last-named day. Sir W, H. M. Ohristie resigned his office on 1910 October 1 …
I,-,Buildings and Grounds,. Movable Property, and Library:-
The principal movable instruments are thus distributed:--
On loan –
One Hilger Chronograph on loan to Professor Turner, Oxford Observatory.
Clocks.-Dent No. 1916 and Dent No. 2013, at the Cape Observatory; Dent No. 2011, at the Kew Observatory; Dent No. 2010, at Devonport; Arnold 2, at the University Observatory, Oxford.
II.-Astronomical Observations:-.
Clocks and Chronographs,- The clock Mudge and Dutton has been repaired during the year, and ,the clocks Molyneux and Dent 2017 are now in the hands of Messrs, E, Dent & Co. for repair.
VII.-Chronometers, Time Signals, and Longitude Operations:-
The number of Government marine chronometers and watches now at the Observatory is 405, viz., 174 box chronometers, 25 pocket. chronometers, 111 chronometer watches, and 95 hack watches.
In addition to these there are, at the Observatory, 7 box chronometers and 2 watches being tested after repair for the Indian Government.
There are also 19 hack watches and 3 chronometer watches on trial for purchase by the Admiralty.
In the year ending 1911 May 10, the average daily number, of chronometers and, watches being rated was 550, the total number received was 1,672, the total number issued was 1,732, and the number sent for repair 744. This last number includes 25 box chronometers, 1 pocket chronometer and 4 watches belonging to the Indian Government.
For the annual trial of chronometers, which lasted 29 weeks with a range of temperature from 47° to 107°, 62 chronometers were sent in. During the trial 28 were rejected, because the difference between one week's rate and the next exceeded 12 seconds. Of the remaining 34 chronometers, 12 were purchased for the Navy.
The performance of these chronometers was very satisfactory.
For the annual trial of chronometer watches, lasting 16 weeks and including trials in the oven and in positions, 208 watches were entered, of which 77 were classified, and of these 60 were purchased for the Navy. Among the watches classified were 30 with centre-seconds' dials; of these 24 were purchased. There were 14 "Karrusel" or "Tourbillon" watches classified, of which 12 were purchased. The performance of the watches was exceptionally good.
A trial of pocket chronometers took place concurrently with the trial of chronometer watches, and under the same conditions as regards duration of trial, temperatures, and positions. Of the 15 pocket chronometers sent in, 3 were purchased for the Navy.
The next trial of box chronometers will commence on June 17, and of pocket chronometers and chronometer watches on July 31.
Since 1905 November, watch makers have been permitted to send hack watches for trial at any time. On receipt at the Royal Observatory they are at once rated under certain conditions, and those coming up to the required standard are purchased for the Admiralty, Altogether 420 such watches have been submitted, and of these 204 have been purchased. There are at present 19 under trial, A trial of non-magnetic watches took place concurrently with and under the same conditions as the chronometer watches. Eight were sent in for trial and 4 were purchased.
To obtain data as to the relative performance of ordinary and non-magnetic. watches in the actual conditions of service a number of watches of both classes were under the Hydrographer's direction specially rated on submarines.
Experiments on the effect of a strong magnetic field on non-magnetic watches have been made and are still in progress at the Royal Observatory.
Provision is now being made to receive and test two classes of non-magnetic watches at the Royal Observatory, (a) those comparable with chronometer watches and (b) watches less highly adjusted.
(a) A trial of non-magnetic chronometer watches will take place under the same conditions as last year, but, in addition, those coming up to the standard tor chronometer watches will be further tested in a strong magnetic field.
(b) The less highly adjusted non-magnetic watches may be sent to the Royal Observatory at any time by the makers. They will be rated for a period of six weeks, including two weeks in the oven. Those coming up to the necessary standard will then be tested in a strong magnetic field.
Since there has been of recent years a large increase in the number of electric motors and other sources of magnetic disturbance on board the ships of His Majesty's Navy, it has become important to determine the minimum distances from such disturbed regions at which chronometers can safely be placed. At the request of the Hydrographer the determination of the maximum intensity of magnetic fields (horizontal and vertical) in which a chronometer may be placed without the alteration in its rate exceeding certain limits is being investigated. Preliminary experiments have been made during March and April 1911, the apparatus consisting of two horse-shoe magnets excited by current drawn from the lighting circuit of the Observatory, suitable resistances being inserted in the circuit. More exhaustive observations will begin shortly with a much larger magnet, consisting of the pole piece of a disused dynamo.
The Greenwich time-ball was not raised on 3 days (December 16, February 22, and March 26) owing to the violence of the wind.
The automatic drop of the Deal time-ball failed on 11 days owing to interruptions of the telegraphic communications. On December 12, the current was too weak to drop the ball. On 5 days the time-ball could not be raised on account of the violence of the wind. Return signals have been received daily except on 26 days.
The return signal from Devonport failed on 64 days (of which 12 were Sundays), and could not be observed on 21 days (of which 7 were Sundays) owing to interruptions by telegraph signals. The apparent error of the clock signal (after daily correction of the clock by aid of a time signal from Greenwich, on the plan described in the Report for 1885) did not exceed 0s.2 on 88 per cent. Of the 279 days of observation, and did not exceed 0s.5 on 97 per cent. On 9 occasions it exceeded 0s.5, but never exceeded 1s.o. The average error for the year was ±0s.12.
The return signal from Portsmouth failed on 61 days (of which 30 were Sundays), and could not be observed on 16 days (of which 7 were Sundays) owing to interruptions by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed 0s.2 on 79 per cent. of the 288 days of observation, and did not exceed 0s.5 on 98 per cent. On 6 occasions it exceeded 0s.5, but never exceeded 1s.0. The average error for the year was ±0s.18.
The return signal from Portland failed on 96 days (of which 49 were Sundays or Holidays), and could not be observed on 14 days (of which 7 were Sundays), owing to interruptions by telegraph signals. The apparent error of the clock (corrected in the same manner as the Devonport clock) did not exceed. 0s.2 on 87 per cent. Of the 255 days of observation, did not exceed 0s.5 on 97 per cent., exceeded 0s.5 on 7 occasions,. on one of which it was over 1s.0. The average error for the year was ±0·s.14.
The automatic signals from the Westminster clock have been received regularly since the last Report. On 14 days the signal failed, and on 9 days it was interrupted by telegraph signals. Its apparent error was not greater than 0s.5 on 46 per cent. of the days of observation, not greater than 1s.0 on 77 per cent., not greater than 2s.0 on 95 per cent. The error was between 2s and 3s on 10 occasions, but never exceeded 3s.5.
It has been found desirable to have a permanent record of the time and duration of time-signals, and a small Krille Chronograph has been brought into use to register the outgoing signal and the returns from Deal, Portsmouth, Portland and Devonport.
Three gentlemen have spent a short time at the Royal Observatory during the year in order to gain knowledge or certain parts or the work. Mr. B. F. Bawtree, Assistant in the Nautical Almanac Office, attended from October 25 to November 8 for the purpose of making himself better acquainted with the manner in which predictions made in the Nautical Almanac are dealt with at the Observatory. Lieutenant A. J. Coleman, R.N., Harbour Master at Singapore, attended from November 15 to January 24 to learn the use or the transit instrument in making time determinations, to enable him to take charge of the time-ball there. Mr. Royds attended from December 5 to December 19, prior to taking up his appointment as Assistant Director at the Kodaikánal Observatory.
VIII.--Personal Establishment:-
| Branch | Assistants | Established Computers | Supermumerary Computers | |
| Time Signals, Chronometers, and 28-inch Refractor. |
Lewis | Bowyer | *Shepperd, *Green, Newton. |
* Qualified as Observers with one or more of the instruments.
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