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 sections dealing with different topics. Both the number of sections and their names evolved over time, some of which are of no relevance here. The extracts for the years 1837–39 come from a paragraph at the end of the reports. In later years such comments were published in a separate section with the heading General Remarks.
Whilst every effort has been made to check for inadvertent omissions and transcription errors, the text is not guaranteed error free. All the reports as published can be accessed on-line via this link.
The only remaining subject, in the general business of the Observatory, is the care of chronometers. I have on a former occasion expressed to the visitors my belief, that the oppression of business arising from the care of chronometers has been most injurious to the astronomical efficiency and general reputation of the Royal Observatory: and I take this opportunity of repeating that belief. I also beg to remark, that this oppression has not been produced by that part of the business which relates to the rating or reporting upon or experimenting upon chronometers, but by that which relates to the money accounts, the accounts of chronometers in store, &c., and the delivery of chronometers to ships. At my representation, alterations have been made in several of the arrangements, the effect of which has been to diminish in some degree the various interruptions to the astronomical business of the place. If at any subsequent time it should be necessary for me to request an expression of opinion from this Board, I trust that I may represent their sentiments correctly by saying, that the persons of this establishment are astronomical observers and calculators, not clerks; that the Observatory is an astronomical institution, not a storehouse; and that any regulation which makes the account-keeping and store-keeping department predominant over the astronomical is an unjustifiable and injurious diversion of its powers.
From the foregoing statement the Board will be enabled to form a pretty correct idea of the history of the Observatory and the Astronomical Work done in it during the last year. There is however one other subject which I mention merely because, if it were omitted, an inadequate notion might be formed of the labour actually borne. It is the daily comparison and official work relating to the Government Chronometers. In bringing this before the Board I have no purpose except to remind them, that our establishment is not wholly devoted to Astronomy, and that our efficiency is weakened by this cause in the part where it is weakest without it, namely, in the force which can be employed on reductions and calculations generally.
As a general remark, I have only to add, that I find the establishment of assistants by no means too strong for the work of computation which is required of them. To their industry and general good conduct I have great pleasure in giving the strongest testimony. The occasional work, however, of the Observatory is not inconsiderable: the number of chronometers on trial in the past spring was greater than usual: my own employments as a public officer have in some degree increased: and upon the whole, it will be seen that our reductions have hardly kept up to our observations. The Board of Admiralty have however for the present allowed me an additional clerk: and with this assistance, I hope that before long we shall be well delivered from the present pressure of business.
I ought not to omit that, though much of the chronometer-business, which withered the power of the establishment during Mr. Pond's presidency, has been removed, still the daily comparison and regular report of numerous chronometers (seldom so few as forty), occupying two assistants for about two days in each week, are no inconsiderable retardation of the business of the Observatory. These causes appear amply sufficient to explain why our reductions can hardly be kept up to our observations. I do not, however, wish at present to call on this Board for additional assistance. After the experience of another year I shall probably be able to state more distinctly, whether in my judgment a greater force of computers is necessary in the Observatory.
5. Instruments. –
… The old Hardy's escapement of the Transit Clock was demanded by the Board of Admiralty, and has been sent to them accordingly.
At the last Meeting of the Board I was desired to consider the facilities or advantages of managing the raising and dropping of the Time Signal Ball by clock-work. I duly considered this matter, and, ultimately, communicated my opinion upon it to one of the Members of the Board; who, as I believe, is disposed with me to abandon the idea. I shall be happy to explain to the Members of the Board the reasons upon which this conclusion is founded.
9. Chronometers. –
The work relating to Chronometers has, in the spring of the present year, been unusually severe; more than eighty chronometers having been on hand, for daily comparisons, through nearly the whole time.
5. Instruments. –
… The old clock for observing Right Ascensions in Arc, presented (I believe) by Sir George Shuckburgh, has lately been put in order.
The three large models of Chronometers, constructed by Harrison, which have been in the hands of Messrs. Arnold and Dent some years for examination and repair, have been restored to the Observatory. A detailed description of them, with elaborate plans, was transmitted by Messrs. Arnold and Dent to the Lords Commissioners of the Admiralty; by whose command the description and plans were lodged in the Safe-Room of the Observatory.
9. Chronometers. –
The number of chronometers on hand for constant rating, from the beginning of the present year, has usually exceeded one hundred. When it is considered that each of these is rated twice every day, that the rates are regularly reported in duplicate, and that besides this there is the whole charge of selection of chronometers for purchase, and of repairs of the Government chronometers, with occasional trouble in the issues of chronometers to the navy, it will be acknowledged that the labour of this department is a fearful load upon the energies of the Observatory. I do not speak of this with any bitterness, for the arrangements made by the Lords Commissioners of the Admiralty and by the Hydrographer, since my accession to this office, have removed several of the inconveniences which caused so much personal annoyance to myself, and interfered so severely with my personal attention to the Observatory: but I am desirous that it should be known to this Board, and to the scientific world , that our establishment of Assistants, nominally large, is really not large and that about one-third of our whole strength is employed upon the business of chronometers.
It was understood last year to be the wish of this Board, that steps should be taken for making public the relative merits of different chronometer-makers. For this purpose, two measures have been undertaken under my direction. The first is, the printing of an abstract of the rates of all the chronometers purchased by the Board of Admiralty, digested in the form in which I had usually arranged them for assisting my own judgment. This was done after the annual purchase in August last; and I propose, if it is approved by the Board, to continue it in future. The second measure is, a digest of the expense of repair of every chronometer whose repairs have passed through my hands. This has not been pressed, as it is hardly possible that the experience of this number of years can afford sure grounds for discrimination among the different makers: but the Board will see, from the prepared books now placed before them, that all the preliminary arrangements are completed and can be followed up at any time.
11. Personal Establishment. –
… The Board of Admiralty, on my representation of the interruption to our business caused by the labour of rating so many chronometers, and by my own employment on public business unconnected with the Observatory, immediately sanctioned the employment of an additional computer; and by his assistance only we have been able to keep the reductions to their present advanced state.
9. Chronometers. –
The oppression from Chronometers in the year since the last Visitation has been beyond all precedent. We have usually been pretty free from Chronometers in the autumn; but in the last autumn the demands of the naval service required the immediate purchase of a considerable number of chronometers, and, in consequence, our Chronometer-room has been constantly full. In the present spring, the number of Chronometers on hand for daily rating has been one hundred and seventy; it is now reduced to about one hundred and thirty. The rating and reporting on these Chronometers occupies very nearly the whole computing time of three assistants.
The abstract of rates of purchased Chronometers, alluded to in the report of last year, has been continued. The digest of the expense of repair has been completed, and is now kept up.
Considerable attention has been paid to the comparison of irregularities in the rates of Chronometers, especially as depending on temperature. Great certainty will be given to all determinations of this nature at the Royal Observatory by the use of a Chronometrical Thermometer (a Chronometer with the laminæ of its compensation bar reversed), suggested and constructed by Mr. R. Molyneux, which gives with the greatest delicacy the summation of the daily or weekly effects of temperature.
An account of constructions, proposed by Mr. Eiffe and Mr. Molyneux, for the correction of Chronometers at extreme temperatures, has been printed under my superintendance. The interest which this inquiry has excited among Chronometer-makers will lead, I am persuaded, to the most beneficial results in the construction of these important instruments.
12. General Remark. –
… To say nothing of the loss, from ill health, of the services of most efficient assistants, I am certain that the quantity of current work will amply explain any backwardness. Perhaps I may particularly mention that in the Observations of 1840, there was an unusual quantity of equatoreal observations, and the reductions attending these occupied a very great time. But, as regards myself, there has been another cause. The reduction of the Ancient Lunar and Planetary Observations, the attention to Chronometer constructions, the proposed management of the printing of papers relating to important operations at the Cape of Good Hope; these and similar occupations have taken up much of my time.
5. Instruments. –
… In my Report for the year 1840, I stated to the Visitors that the escapement of Hardy's Clock had, by command of the Board of Admiralty, been delivered to the Secretary of the Admiralty. The long detention of this apparatus makes me anxious now for its return.
8. Printing. –
… On referring to the published volume for 1841, it will be seen that the results of rating the Chronometers on trial have been printed in a more extended shape than in former volumes.
9. Chronometers. –
The number of Chronometers on trial in the present year is considerably less than in the last year.
In my last Report, I stated the probability that great interest would be excited among Chronometer makers by the publication of the account of Eiffe's and Molyneux's construction of Chronometers. This expectation has been fully borne out: many different schemes for the same purpose having been proposed to the Hydrographer and to me. The necessity of subjecting Chronometers, constructed on these principles, to trials in extreme temperatures, has led me to make arrangements for heating the Chronometer- room, and thereby rendering ourselves comparatively independent of the season, at least as far as warmth is concerned.
The Digest of the Estimates of Expense of Repairs to Government Chronometers has been regularly kept up, in obedience to the directions of the Board.
1. Grounds and Buildings. –
The Visitors may have remarked, also, a small building containing a pier of brick and, tone, adapted for observations with a portable transit, which is now erected on the Magnetic Ground. This has been erected for the observations which Mr. Struve is about to make, for determining, by transmission of chronometers, the difference of longitude between Greenwich and Altona, as part of the difference of longitude between Greenwich and Pulkowa. Mr. Struve's plan, of interchanging the observers at the two ends for the elimination of personal equation, makes it almost necessary that he should have the complete command of a transit instrument; but the combination of the observations made at this instrument with those made by our own observers with our own transit will be extremely easy. Mr. Otto Struve has already arrived to make the first preparations, and to conduct the first half of the observations; and I expect to be honoured with a visit from Mr. Struve himself, as soon as the regular interchange of chronometers shall have commenced.
5. Instruments –
… The escapement of Hardy's clock has been returned by the Secretary of the Admiralty.
8. Printing . –
The Astronomical volume for 1842 is lately finished; its form is precisely the same as that of the volume for 1841, excepting that it has, as Appendix, the Catalogue of 1439 stars. The volume contains , as usual, the results of rating the Chronometers on trial, and the last Report of the Astronomer Royal.
9. Chronometers . –
The number of chronometers on trial during the last year has not been excessively great. At present there is a considerable number (about one hundred and ten); many Government chronometers having been returned from ships paid off, and about thirty chronometers being rated in preparation for the determination of the longitude of Valentia in Ireland.
The Digest of the Estimates of Expense of Repairs to Government Chronometers is still kept up.
12. General Remarks. –
… But at the same time it will be gathered that, in the occasional employments of myself and my assistants, many things are included, occupying much time, … Aiding Mr. Struve in his proposed determination of the longitude of Pulkowa. Arranging an enterprise to determine the longitude of Valentia in Ireland, for the measure of an arc of parallel, and for the fixing of a nautical zero. For several of these purposes I have had to ask the assistance of other persons or establishments.
I. Grounds and Buildings. –
... The small Observatory, upon the Magnetic Ground, intended for Mr. Struve's use, which was already erected at the last Visitation, and which was employed for its original purpose during the last summer, has since that time been unoccupied. I propose, however, to retain the building in its present state until some strong reason for its removal shall present itself, as it is sufficiently probable that occasions may again arise requiring the use of a portable transit instrument.
2. Moveable Property in General. –
The whole of the moveable property entered in the Observatory catalogues is now, I believe, at home and in good order, with the exception only of a Journeyman Clock, which has not been used for at least ten years, and which I have lent to the Kew Observatory, to be used in conjunction with the electric apparatus mounted there.
9. Chronometers . –
The number of Chronometers at the Observatory, whose rates have been regularly taken during the last year, is about the average, the number being some-times above one hundred, but more frequently below it. These Chronometers are compared every day by two assistants, at a small interval of time, and their rates are reported every week to the Hydrographer. Special comparisons are made on the occasion of issues of Chronometers to ships. The superintendance of the repairs of all Government Chronometers is managed solely by myself and the First Assistant.
The Signal Ball is dropped precisely at one o'clock on every day, Sundays as well as week days.
These operations, with all the comparisons of clocks, changes of sidereal time to mean solar time, and other calculations which they imply, occupy a very great part of the strength of our stablishment.
An Abstract of the Rates of Chronometers on Trial for Purchase is printed, and is attached to the volume of Astronomical Observations. The Abstract of the Rates found in the trial of 1844 is attached to the Observations of 1843.
The Digest of the Estimates of Expense of Repairs to Government Chronometers is kept up in manuscript, but is not printed. It is nearly complete to the present time.
10. Personal Establishment. –
… The Assistants of the Astronomical Department are charged with all work relating to the Chronometers and Signal Ball, and with the care of Stationary Stores; those of the Magnetical Department with the care of the Manuscripts and Library.
12. General Remarks. –
The Royal Observatory, and the persons connected with it, are not, in my opinion, rendering their best service to the country by confining themselves to the observations made in one building upon one system, although, in any case, these observations ought to have by far the most important part of their energies; and any other work to which they may give their remaining strength ought to be strictly related to their primary object. It will be found, I trust, that these principles have been kept in view in the deviations from our ordinary system, which I am about to mention. Some small interruption (bearing no comparison with the advantage which we derived from it) was caused by Mr. Struve's operations in the summer of 1844, for the determination of the longitude of Altona, by the transmission of chronometers. This determination was completed in the most satisfactory manner. The chronometers, forty-two in number, crossed the German Sea sixteen times. The transit observers were twice interchanged, in order to eliminate not only their personal equation, but also the gradual change of personal equation. The definitive result, as I understand from Mr. Struve, scarcely differs from that which had been obtained several years before by far less adequate means, a coincidence which of course is accidental as regards the older result. An expedition, which (with the assistance of Mr. Sheepshanks ) I had planned for the determination of the longitude of Valentia , in Ireland , and for the incidental determination of the longitude of Liverpool and of Kingstown (by Dublin) , was executed in the last summer, by the assistance of the Birmingham and Grand Junction Railway Companies, the Mail Packet Superintendant, and the Proprietors of the Contract Mail Packets between Liverpool and Kingstown, the Inspector of Mail Coaches in Ireland , the Inspector of Coast Guard, the Master- General of the Ordnance, and especially Colonel Colby , and the able and zealous officer ( Lieutenant Gossett, R. E. ) who was stationed at Valentia, but above all by the unwearied personal assistance of Mr. Sheepshanks. Upon the failure of Mr. Sheepshanks' health, from extreme fatigue and exposure, I sent Mr. Hind (then one of the Assistants on the Magnetic establishment) to Kingstown to take his place. Thirty pocket chronometers traversed the line between Greenwich and Kingstown about twenty- two times, and that between Kingstown and Valentia twenty times. The results are most satisfactory as regards the weight which they deserve, and are interesting as compared with the deductions from the geodetic survey which connects all the points. The chronometrical longitudes of Liverpool Observatory, Kingstown Station , and Valentia Station , are 12m.0s.05, 24m.31s.17, 41m.23s.25 ; the geodetic longitudes, computed from elements which I published long ago , in the Encyclopædia Metropolitana, are 12m.0s.34, 24m.31s.47, 41m. 23s.06. It appears from this that the elements to which I have alluded represent the form of the earth here as nearly as is possible, and at the same time that there is a center of disturbance somewhere in the eastern part of Ireland: which, geologically, seems sufficiently probable. It is certain that there is no error of azimuths which can account for the small discrepancy at the two intermediate stations, because the calculated and the observed latitude of Valentia agree accurately. On the whole, I think it probable that this is the best arc of parallel that has ever been measured.
2. Moveable Property. –
One of our journeyman clocks has been lent to the Observatory of Kew for use, and one magnet for experiments on the practicability of introducing self-registering apparatus for magnetometers.
9. Chronometers. –
The number of Chronometers in the last year has been about the average. As before, they are usually compared twice each day, and their rates are reported to the Hydrographer. An Abstract of the Rates of Chronometers on Trial for Purchase is attached to each annual volume of Astronomical Observations.
The repairs of Government Chronometers are superintended by myself. A Digest of the sanctioned Estimates is kept in manuscript.
The Signal Ball is dropped by an Assistant at one o'clock precisely every day. Its fall is always observed by another Assistant. The error of time does not usually exceed one-tenth of a second, and does not amount to three-tenths of a second oftener than once in six weeks.
2. Moveable Property. –
Our moveable property is entirely at home, with the following exceptions :-
One Journeyman Clock, and one Bar- Magnet- lent to the Observatory of Kew. …
Two Chronometers, by Massey, for measuring small portions of time – delivered, by instruction from the Admiralty, to Sir James South. …
I have the gratification of announcing to the Visitors that a very valuable present has been made to the Observatory. In the summer of last year it was notified to me by the Rev. Charles Turnor (in the first instance through Captain Smyth, R. N.) , that he was desirous of presenting to the Royal Observatory an excellent clock, made by Mudge and Dutton . No present could be more acceptable to me, more especially at a time when I was contemplating the speedy mounting of a new instrument. I lost no time in stating this to Mr. Turnor; and the clock was very soon brought to the Observatory, and there mounted, without any expense to the Observatory. It appears to be going extremely well. I am confident that the Visitors will with me appreciate not only the value of the present, but also the manner in which it was made.
9. Chronometers. –
The number of Chronometers during the last year has been nearly the average. At this time the number is large: in the present week the number rated was 117. The rating and reporting on these, the management of repairs, and other business relating to them, occupy a portion of our energies, for which the Observatory does not receive sufficient credit. I consider that, on the whole, the computing time of more than one assistant is absorbed in this work.
The Abstract of the Rates is printed, the manuscript Digest of Estimates is kept up,
and the affairs of the Signal Ball are managed as in the last year.
2. Moveable Property. –
The moveable property of the Observatory is generally in good order ; and is entirely at home, with the exception of the following articles :-
One Journeyman Clock and one Bar- Magnet- lent to the Observatory of Kew. …
Two Chronometers, by Massey, for measuring small portions of time delivered, by instruction from the Admiralty, to Sir James South.
13. Chronometers. –
The number of chronometers now on hand for rating is 95 , which is rather less than the average.
The Abstract of Rates and Digest of Estimates are maintained in their usual form.
The Signal Ball is dropped regularly, and its error is registered, at one o'clock every day.
II . Moveable Property. –
Our Moveable Property, instrumental and domestic, is generally in good order. The Journeyman Clock and Bar Magnet lent to the Observatory at Kew; the copy of Piazzi's Catalogue lent to the Observatory at Durham; and the two Massey Chronometers, delivered by Admiralty Order to Sir James South, are still out of our hands.
III. Chronometers.–
Under this head I have no special remark to make . The routine of rating, abstracting the rates, abstracting the expenses, dropping the signal ball &c., goes on as usual. The number of chronometers on hand for rating at the present time is 98, of which the greater part are rated daily, the remainder weekly.
XVI. General Remarks. –
Another change will depend on the use of galvanism ; and, as a probable instance of the application of this agent, I may mention that, although no positive step has hitherto been taken, I fully expect in no long time to make the going of all the clocks in the Observatory depend on one original regulator. The same means will probably be employed to increase the general utility of the Observatory, by the extensive dissemination throughout the kingdom of accurate time-signals, moved by an original clock at the Royal Observatory ; and I have already entered into correspondence with the authorities of the South Eastern Railway (whose line of galvanic communication will shortly pass within nine furlongs of the Observatory,) in reference to this subject. The policy of using galvanism in the way lately proposed in America, for the register of transit-observations, is perhaps doubtful, except in very peculiar cases.
I allude to these subjects, however, with the hope of conveying this idea to the Visitors: that while, on the one hand, the general steadiness of plan of the proceedings at the Observatory is, as I trust, sufficiently proved by the account which I have exhibited of what has been done, and what is still to be done ; on the other hand, there is no disposition to allow this institution to remain stationary in merit, while others are advancing.
For several reasons, it is convenient to terminate the Report with the end of a lunation; and it is therefore to be understood generally that the account now presented to the Visitors applies to the state of the Observatory on May 11.
II. Moveable Property. –
Every thing remains nearly in the same condition as at the last Visitation.
XIII. Chronometers. –
The chronometers are compared as in preceding years (except that, when there is no special reason for requiring two comparisons, one daily comparison only is taken, and sometimes only one weekly); their rates are reported and abstracted, the expenses of repairs are digested, the signal–ball is dropped, &c., as in former years. The number of chronometers now on hand is 112.
I am preparing an apparatus for heating the trial-chronometers by the flame of gas, in nearly the same manner which has been adopted with great convenience at the Liverpool Observatory.
XVI. General Remarks. –
The matters to which I desired to invite the attention of the Visitors have been so completely embodied in the classified statements already read to them, that I have little of miscellaneous character to subjoin. Many arrangements, it will easily be understood, are waiting for the erection of the large Meridional Instrument. Still there are two points which have distinctly engaged my attention, and which I propose to urge as occasion serves, unless I shall see new reasons for doubting their propriety.
The first of these is, the introduction of the American method of observing transits, by completing a galvanic circuit by means of a touch of the finger at the instant of appulse of the transiting body to the wire of the instrument, which circuit will then animate a magnet that will make an impression upon a moving paper . After careful consideration of this method, I am inclined to believe that, in Professor Mitchell's form, it does possess the advantages which have been ascribed to it, and that it may possess peculiar advantages in this Observatory, where the time- connexion of transits made with two different instruments (the Transit and the Altitude and Azimuth) is of the highest importance. But on the other hand this peculiar circumstance introduces special difficulties: for it makes it impossible for us to confine the time of use of the apparatus to the mere time of observing a series of transits (as is in the power of a dilettante observer), and the consumption of recording surface must be very great. Moreover, it will not be easy to arrange the times of gearing and ungearing the instrument (in order to save recording surface) so as to consult the convenience of both observers. In considering these things, it has appeared to me that the first point at which it is desirable to aim is, to produce a very uniform movement of the recording surface, even sufficiently perfect to enable me, if I shall think fit, to use that movement for the record of time instead of the usual detached sidereal clock ; and I have mechanism now in progress, depending for its regulation on the motion of a nearly free conical pendulum in an arc whose radius does not exceed two degrees, by which, even when resistances are exceedingly variable, I almost hope to accomplish this object. I alluded in my last Report to the possible galvanic connexion of the different clocks of the Observatory, so as to make the motion of every clock depend on the motion of one: but I am now inclined to think that there is a better prospect of advantage in the American system of registering the observations made at different parts of the Observatory on one recording surface.
The second point is, the connexion of the Observatory with the galvanic telegraph of the South Eastern Railway, and with other lines of galvanic wire with which that telegraph communicates. No arrangement is yet effected for this purpose, but I continue to keep my attention on it, even with greater interest than formerly. I had then in mind only the connection of this Observatory with different parts of the great British island: but I now think it possible that our communications may be extended far beyond its shores. The promoters of the submarine telegraph are very confident of the practicability of completing a galvanic connexion between England and France: and I now begin to think it more than possible that, within a few years , observations at Paris and Brussels may be registered on the recording surfaces at Greenwich, and vice versâ.
THE Report which I have the honour now to present to the Board of Visitors is intended to convey an account of the state of the Royal Observatory on 1851, May 30; and of the proceedings in the Observatory from 1850, May 11, to that time.
I. Grounds and Buildings . –
The ground- floor room of the North Dome (formerly called the East Dome, and lately the North-east Dome) was for more than half a century useless, because it was used as a passage-room. A most insignificant alteration of doors and windows, effected about two years ago, made it available as a separate room, with convenient access. For some time past it has been destined to contain the Galvanic Registering Apparatus to be employed on the American principle, for recording the Transits observed with the Transit- Circle and the Altazimuth; and in the last year the basement has been prepared (by inserting windows, paving the floor, and placing a ladder) for the Galvanic Batteries and other rough apparatus required in the American register. The rooms, however, are not yet occupied.
It will be necessary soon to increase our Library accommodation; and I have begun to make preparations for this extension, by removing the Chronometers from the room which they have many years occupied (adjoining the Library) to a room above the Computing Room, formerly used as an Assistant's sleeping-room, but for many years past nearly useless. The Old Chronometer Room is at present used for a temporary purpose, but I intend before long to fit it up with Library Shelves. The New Chronometer Room is somewhat larger than the old one, and it is furnished with an apparatus for warming a limited number of chronometers by the heat of gas-flames, copied from that established in the Liverpool Observatory. Adjoining to the Chronometer Room is a small room now used as Office for the transaction of Chronometer Business.
Gas illumination has now been introduced in all the buildings and on all the instruments, as far as I think it desirable to employ it.
V. Astronomical Instruments. –
Both the Transit-Circle and the Altazimuth are fitted up with galvanic wires and contact-apparatus for making a galvanic register of transits in the American manner, and the wires are led into the ground-floor story of the North Dome. The reading- barrel and the registering apparatus, however, are not yet mounted. I may state to the Visitors that I hope to mount an apparatus which shall cause a barrel to revolve with Astronomical uniformity, using a mercurial pendulum revolving in a cone of about two degrees' radius, which is resisted only by the air, and introducing in the machinery which acts upon this a modification of the Chronometric Governor, applicable to the regulation of machines driven by weights. I have tried this carefully in experiment, and have reason to believe that it will act very well. The clockwork for the new machinery containing this principle is completed by Mr. Dent; but the barrels and galvanic apparatus are not yet completed by Mr. Henley, to whom that part of the work is intrusted.
XIII. Chronometers. –
The chronometers are compared as is described in last year's Report, some every day and some once a week, as the object of their comparison appears to require ; their rates are reported every week to the Admiralty ; and an Abstract of the rates of those on trial for purchase , is circulated among chronometer-makers and others, and is attached to the volume of Observations. The repairs of Government chronometers are made entirely under my superintendence. The expenses of repairs are digested for our own reference, but are not printed. The number of chronometers now on hand is 96.
Since the commencement of the present year, the gas-heating apparatus has been employed for those chronometers which were to be tried in elevated temperatures.
The signal-ball is dropped at one o'clock every day by one Assistant, another Assistant being employed at the same time to observe and register the time of its fall. I am thus in a condition to exhibit the absolute error in the time of its drop; it is usually a very small fraction of a second of time.
THE Report now laid before the Board of Visitors embraces the history of the Observatory during the twelve lunations from 1851, May 30, (the epoch of the last Report), to 1852, May 18, and applies to the state of the Observatory on the day last mentioned.
I. Grounds and Buildings. –
The Old Chronometer Room has been fitted up with shelves for increase of Library accommodation, and one extensive class of books (Transactions and Serial Works) has been removed to it.
On the outside of the Observatory fence, however, an important work has been executed. In the last and in preceding Reports, I had alluded to the probability of our requiring, in no long time, a galvanic connection with London and with the Continent of Europe. In the last autumn, the Submarine Telegraph between the South Foreland and Sangatte, in France, was successfully completed, and in a very short time afterwards I received from some of the active members of the Institute of France an earnest request that advantage might be taken of this event for connecting the Observatories of Paris and Greenwich. I proceeded without delay to negotiate with the great commercial bodies (the Electric Telegraph Company and the South-Eastern Railway Company) whose assistance was necessary, and whose rights might be affected by such a connection; and by them my overtures were received in the most liberal spirit. To these bodies generally, and to their Superintendants of Telegraph in particular (Charles V. Walker, Esq., for the South-Eastern Railway, and Edwin Clark, Esq., for the Electric Telegraph Company), my most cordial thanks are due, for their adoption of my proposals in all their fulness, and for their hearty co-operation in every part of the work. The Lords Commissioners of the Admiralty at once made provision for carrying out this plan, which had not been foreseen in time for inserting a proper sum in the Navy Estimates. The result is, that four insulated wires are laid in the ground, at depths varying from three to five feet, on a line commencing at the ground-floor of the North Dome (now called the Galvanic Room), across the Front Court, along the centers of the great avenues of the Park to the southern gate in the western wall of the Park, and by the south-east side of the road leading thence across BIackheath to the Lewisham Station; from which point two wires are carried, sometimes on poles and sometimes in grooved boards, to the London-bridge Terminus, where the connections will be made, either with the long Dover wires communicating with the Continent, or with the wires which extend to the Central Telegraph Station. These connections are not yet made.
V. Astronomical Instruments. –
The apparatus for uniform movement of a barrel, upon which records of transits are to be made by an impression produced by a galvanic current whose circuit is completed by an observer at the Transit-Circle or the Altazimuth, after delays of which I could form no anticipation, is now nearly prepared by Mr. Henley for work. I almost fear, however, that I shall not be able to exhibit it to the Visitors in motion. The galvanic connexions, the batteries, &c., are not yet ready; and some time must elapse before the American system can be fairly tried. The clock-work for driving· the Barrel has long since been prepared by Mr. Dent; and I trust that I may be able to point out to the Visitors the peculiarity of its principle.
I have stated in former Reports that I contemplated as one of the uses of a galvanic connexion with the Central Telegraphic Station in London, the transmission of signals of accurate Time. For this purpose, it was necessary to be furnished with a Clock, possessing these two properties; that it can be made to exhibit accurate time, and that it can complete galvanic circuits at certain determinate instants of that time. Mr. Shepherd of Leadenhall-street has undertaken the construction of a clock which shall possess these properties. The former condition will be obtained by a mechanical action on the pendulum, which will correct it for an error (as ascertained by transits) of even a small fraction of a second. The latter will be effected by breaking the galvanic circuit at three places, all which must be closed simultaneously for the transmission of a signal; and by closing one of the breaks by the minute wheel, one by the hour wheel, and one by the 24-hour wheel. This system being supposed established, it occurred to me that with very little trouble it might be so extended as to give movement to a number of sympathetic galvanic clocks, everyone of them exhibiting accurate time, in various parts of the Observatory. I have, therefore, arranged for the exhibition of accurate time for the use of the public on a large external dial near the Entrance Gate; for time in the Chronometer Room (where for convenience the clock will be made to admit of azimuthal movement round a vertical spindle), so as to enable us to dispense with comparisons and to escape the necessity of correction for clock-error; for time in the Computing Room; and for time in my own residence.
XIII.-Chronometers. –
In respect of the daily and weekly rating of chronometers, the weekly report to the Admiralty, the annual Abstract of rates of those chronometers which are sent on trial for purchase, the digest of expenses of repairs made under my superintendance, the use of the gas-apparatus for heating chronometers, and the daily dropping and observation of the signal-ball, there is no alteration of system since last year. The number of chronometers now on hand is 113.
The promotion of the means of obtaining accurate time, either by supplying the grounds for indisputable judgment on the relative merits of competing chronometers, or by exhibiting to the public (domestic as well as nautical and horological) signals for the indication of exact instants of time, has been recognised by all the authorities of the Observatory as an important part of the every-day utility of this institution. I trust, therefore, that the measures now undertaken for the dissemination of time-signals on the telegraph-lines, and for the exhibition of time on the Observatory walls, will meet with the approbation of the Visitors.
XVI. General Remarks. –
Our only instrumental novelty in the past year consists in the establishment of our galvanic connections; and these appeared to be imperatively required by the advances of practical art and by the demands of science and of society.
In my last Report to the Board of Visitors, I brought up the account of the Observatory to 1852, May 18. In the present Report I propose to exhibit the state of the Observatory on 1853, May 22, and to record generally the principal occurrences from 1852, May 13, to 1853, May 22.
I. Grounds and Buildings.–
Beyond our own boundaries, however, there are two things worthy of mention to the Visitors. … The second point is, the state of our galvanic communications. At the date of my last Repot, the principal part of the work for carrying two wires to London Bridge (four having been laid in those parts in which the wires pass underground), was, by the kindness of the South-Eastern Railway Company and the Electric Telegraph Company, completed, but the wires were not so far connected as to be brought into use. Shortly after that time they were brought into daily use. Our prospective wants of galvanic connexions are increasing, and I have lately received the sanction of the Admiralty for the principal measures necessary to establish four complete galvanic lines from the Observatory to London Bridge.
One of the objects which it was proposed at first to effect by making a galvanic connexion with the London Bridge Railway Terminus was, to secure a communication with the Submarine Telegraph, and thus with the Continent of Europe generally, and with Paris in particular. There was reason at that time to expect that the Dover Railway wires and the Submarine wires would be connected. The commercial relations of the companies, however, underwent some change; and ultimately an entire new line of wires has been laid underground from London to Dover, passing over Blackheath. Upon my communicating with Lord De Mauley and the Directors of the Submarine Company, I was assured by his Lordship that every facility would be given by that Company for communication with Paris, provided the connexions were made directly between the Royal Observatory and the wires of the Company. And the Officers of the Company with great courtesy acceded at once to the plan which I proposed, and which is now carried into execution. One of the Company's wires was cut where it crosses Blackheath, and the interrupted segments were continued by branches to a turn-plate which is contained in an iron box fixed in the south wall of the Park. From this turn-plate, a wire is led into the Transit-Circle-Room of the Royal Observatory. By different adjustments of the turn-plate, communications are made between London and Paris, between London and Greenwich, or between Greenwich and Paris. By a most liberal concession of the Company, the key of the iron box is preserved in my custody. The wire has not yet been used for the Greenwich-Paris communication, for reasons which will be explained shortly. In resuming, I may state that we have now the means of communicating with every part of Great Britain and of the Continent.
V. Astronomical Instruments –
The Barrel Apparatus for the American method of observing transits is not yet brought into use. In an apparatus, embodying much that is new (for the circumstances under which we have to try it differ much from those of the original experiments), there must be a great many small alterations; and sometimes, from the demand for workmen competent to perform work of this kind, a single alteration has caused more than a month's delay. I have, however, brought it to it such a state that I am beginning to try whether the Barrel moves with sufficient uniformity to be itself used as the Transit Clock. This, if perfectly secured, would be a very great convenience; but I am not very sanguine on that point. Much convenience will, however, be gained by making the barrel to move with a speed approaching very near to uniformity, even though the barrel-clock be not quite accurate enough to be used as the best measurer of time in the Observatory, and, therefore, not accurate enough to be used for impressing the second-dots upon the barrel.
The galvanic apparatus for sending hourly signals to London; the sympathetic dial at the Entrance Gate; the sympathetic clocks in the chronometer-room, computing-room, and dwelling-house; and a sympathetic clock at the South-Eastern Railway Terminus, are all complete and in constant use. In the employment of the galvanic wires in-the Royal Observatory for the several purposes of making registers in the American manner, dropping our time-ball, sending hourly signals to London, dropping the ball in the Strand, passing occasional signals to or from London and stations beyond London, and passing occasional signals to or from Paris, a variety of communications of wires is required. These are effected by means of several turn-plates which are distributed in different parts of the buildings.
XIII. Chronometers, Communications of Time, and Operations for Longitude. –
The number of Chronometers now on hand is 120. The system of rating the chronometers daily or weekly as the case appears to require, of reporting the rates to the Admiralty, of rating the trial-chronometers in extremes of heat and cold, of abstracting their rates, of superintending repairs, and of dropping the signal-ball, remains unaltered. In the mechanical part of the operation of rating an alteration has been made, which contributes greatly to convenience, and in some measure to accuracy. At the time of the Vistors' last meeting, a Normal Clock had been erected by Mr. Shepherd, furnished with a small apparatus suggested by myself (an auxiliary pendulum, which can be made very long or very short, and can in either state be connected with the clock-pendulum), by means of which the indication of the clock can be increased or diminished by any required quantity above 0s.01. The error of this clock being ascertained every day, by means of another clock close to its side which has been compared with the Transit-clock, there is no difficulty (with the use of the auxiliary apparatus above mentioned) in making it sensibly correct. This clock keeps in motion a sympathetic galvanic clock in the Chronometer-room, which, therefore, is sensibly correct; and thus the chronometers are compared with a clock which requires no numerical correction. I need not insist on the facility, and the freedom from a fruitful source of errors, which are thus obtained.
The same Normal Clock maintains in sympathetic movement the large clock at the entrance-gate, two other clocks in the Observatory, and a clock at the London-bridge Terminus of the South-Eastern Railway (first tried with the assistance of C. V. Walker, Esq., as an experiment, but now to be used for automatically making and unmaking certain connexions of our galvanic wires). It sends galvanic signals every day along all the principal railways diverging from London. It drops the Greenwich Ball and the Ball on the Offices of the Electric Telegraph Company in the Strand; and the correctness of the last of these operations is tested by means of a galvanic signal-needle upon the case of our transit-clock. All these various effects are produced without sensible error of time; and I cannot but feel a satisfaction in thinking that the Royal Observatory is thus quietly contributing to the punctuality of business through a large portion of this busy country.
I have the satisfaction of stating to the Visitors that the Lords Commissioners of the Admiralty have decided on the erection of a Time-Signal Ball at Deal, for the use of the shipping in the Downs; to be dropped every day by a galvanic current from the Royal Observatory. The construction of the apparatus is intrusted to me. Probably there is no roadstead in the world in which the knowledge of true time is so important; and I anticipate that this decision of the Admiralty will be highly agreeable to the Visitors.
One of the objects, for which the galvanic communications between the Royal Observatory and the principal lines of telegraph were recommended, was the determination of differences of longitude, for British and Continental Observatories. I am happy to state that a step has been made in carrying out this intention. On the nights of May 17 and 18, excellent series of signals were passed backwards and forwards between the Royal Observatory and the Railway Station at Cambridge. No wires have been led to the Cambridge Observatory; and Professor Challis was therefore compelled to carry chronometers, previously compared with the transit-clock, to the station. The observers were interchanged on May 18 for the elimination of personal equation. At the moment of my writing, the observations are not fully reduced; but I shall probably be able to state verbally to the Visitors the result of this operation. I anticipate from it a most accurate determination of the difference of longitude. It is perhaps worthy of mention that all the Greenwich signals were given by the contact-apparatus on the Transit Circle, adapted to the American method of observation; and that many of them corresponded to the transits of stars over the wires, as observed by the eye.
I have also made every arrangement with Professor C. Piazzi Smyth for the interchange of signals on the night of May 25, and trust to be able to state to the Visitors the result.
I believe that wires are nearly completed for connecting the Oxford Observatory with the Railway Station at Oxford, and I may soon anticipate the galvanic determination of the longitude of Oxford Observatory.
In these operations I am gradually acquiring the experience which will be necessary for undertaking an enterprise of somewhat greater difficulty and greater delicacy, namely, the determination of the difference of longitude between the Observatory of Paris and that of Greenwich.
XVI. General Remarks. –
The characteristics of our Astronomical duties are well understood by every Assistant connected with the establishment. It is known that we are confined to observations of a standard class, and that even our galvanic and other novelties are subjected to that restriction; but in that restricted class it is known that our observations must be unimpeachably good.
Addendum. –
I Have the satisfaction of stating to the Visitors, that the galvanic communications with Cambridge appear to have been perfectly successful, and the determination of its longitude most accurate. The atmosphere was in a dry state, which is important for insulation. The number of pairs of plates used at each end was 72. The signals were very strong and definite. On both nights, transits were obtained at both stations, both before and after the signals. The transits were reduced by two methods :-In Method A, the clock-stars of the Nautical Almanac were used; in Method B, a number of other stars (the same at both stations) were used. The result, as supplied to me this day by Professor Challis, is-
East Longitude of Cambridge.
Method A.
May 17. By 145 signals .... 22s.953
May 18. By 134 signals .... 22s.978
Mean 22s.966
Method B.
May 17. By 145 signals .... 22s.903
May 18. By 134 signals .... 22s.988
Mean 22s.946
Concluded mean, giving equal weight to the two methods .... 22s.956
The interchange of signals with Edinburgh also was perfectly successful: 216 pairs of plates were used at Greenwich against 144 at Edinburgh. I am not yet able to give the result for longitude, as there appears to have been an error in a chronometer at Edinburgh which is not yet completely corrected. I am able, however, to state the following result (which is not likely to be altered by correction of the chronometer): that the retardation in the time of observing a signal sent from Greenwich to Edinburgh or from Edinburgh to Greenwich, depending undoubtedly upon the two circumstances of gradual transmission of the galvanic current and more languid movement of the needle at the station furthest from the battery, is +, 1/17 of a second of time.
THE present Report to the Board of Visitors may be understood as recording the general condition of the Observatory on 1854, May 26, and the transactions from 1853, May 22, to that time.
I. Grounds and Buildings.–
Exterior to it [the Observatory], the following particulars require notice. … Four complete galvanic lines are now established from the Royal Observatory to the London Bridge Railway Station. Three of these are appropriated to specific uses; the fourth is reserved for contingencies.
V. Astronomical Instruments.–
The Barrel-Apparatus for the American method of Transits has been practically brought into use: not, however, without a succession of difficulties, arising sometimes from causes very hard to discover. When the instrument was approaching to a serviceable state, there still remained an imperfection in the ill-defined form of the punctures on the paper. At this juncture, Lieutenant Maury, U.S.N., paid me a brief visit, and in the course of inspection of the instruments he alluded to this very defect, and to the method which had been used in America for its remedy. Although my apparatus did not admit of the same application, yet, possessed of the principle, I had no difficulty in embodying it in a form adapted to my wants; the prickers were mounted on springs, and now the punctures are perfectly round. The paper on which the punctures are to be made is folded in a wet state, upon a brass cylinder covered with a single thickness of tailor's woollen cloth, and has its edges united by glue.
The punctures, it will be remembered, are produced by two systems of prickers, which have nothing in common except that they are carried by the same travelling frame, which moves slowly in the direction of the barrel-axis while the barrel revolves beneath it. These require separate notice.
One pricker is driven by a galvanic magnet whose galvanic circuit is completed at every second of sidereal time. It was at first intended by me that the completion of the circuit should be effected by the same smooth-motion clock (regulated by a conical pendulum) which drives the barrel. I found, however, that I could not ensure such a constancy in the radial arc of the pendulum as would make its rate sufficiently uniform to entitle it to be considered as the fundamental clock; and, moreover, there was a little difficulty in referring its indications to those of the transit-clock (which must be used in some cases). I, therefore, carried wires from the pricker-magnet to the transit-clock, connected there with springs whose contact is made at every second by the transit-clock. At first, the contact was made by the touch of a pin fixed in the pendulum-rod; and this construction for a time answered well. But it so happens that, in our transit-clock, the pendulum is carried by one frame, and the point of attachment of the galvanic springs by a different frame: it was impossible to maintain these in steady adjustment; and the rate of the clock was sensibly disturbed. I have now adopted the following construction, which promises to succeed better. A wheel of 60 teeth is fixed on the escape-wheel-axis, and the teeth of this wheel in succession make momentary contacts of the galvanic springs. The position of the springs is so adjusted that the effort of the wheel-tooth upon them occurs only when one escape-tooth has passed the sloping surface of the pallet, and the other escape-tooth is dropping upon its bearing; and thus the resistance of the springs does in no way affect the legitimate action of the train upon the pendulum.
The other pricker is driven by a galvanic magnet, whose circuit is completed by an arbitrary touch made by an observer's finger upon a contact-piece. Of contact-pieces there are three. One is upon the eye-end of the Transit Circle: it effects the contact of two brass rings which (by means of wires passing in the interior of the tubes) are connected with two other brass rings surrounding the axis and touched respectively by two springs on the pier leading to the galvanic wires. The other two contact-pieces are upon the rotating base-plate of the Altazimuth (one to be used with Vertical Face to the Right, the other with Vertical Face to the Left); the parts which they bring together carry springs which touch two large horizontal rings on the fixed base; and these rings are connected with branches of the same pair of wires which communicate with the Altazimuth. Thus Altazimuth observations are referred absolutely to the same time-record as Transit-Circle observations.
It is necessary to mark upon the revolving barrel the beginnings of some minutes and the numeration of some hours and minutes. This is done by arbitrary punctures given by the observer's touch, upon a simple system which scarcely merits detailed description.
In order to guide the eye through the multitude of dots upon the sheet, lines of ink are traced by means of a glass pen, which is attached to the same frame as that by which the prickers are carried.
Wires have been inserted in the wire plates, both of the -Transit Circle and of the Altazimuth, at intervals adapted to the rapid observation by touch. The wires of the Transit Circle and the vertical wires of the Altazimuth are adapted to intervals of about 42” and 48” of arc; the intervals of the horizontal wires of the Altazimuth do not exceed 24” of arc. They are probably the smallest intervals that have ever been used. The old systems of wires are not disturbed, nor rendered confused; so that, with the Transit-Circle, either 7 wires may be observed by ear or 9 by touch; and with the Altazimuth (in either dimension) either 6 by ear or 6 by touch.
I have only to add that this apparatus is now generally efficient. It is troublesome in use; consuming much time in the galvanic preparations, the preparation of the paper, and the translation of the puncture-indications into figures. But among the observers who use it there is but one opinion on its astronomical merits-that, in freedom from personal equation and in general accuracy, it is very far superior to the observation by eye and ear.
The galvanic apparatus for giving time-signals, for dropping the time-ball, and for maintaining the movement of sympathetic clocks, is in the same state as at the last Report, with this addition only: that a separate battery, galvanic needle, and pair of contact springs, are appropriated to the wire on which the current is sent to drop the Time-Ball at Deal at 1h (the contact being completed by the same movement of a galvanic magnet which drops our own Ball), and that the fall of our Ball-Tumbler then effects such a change in the connexions of the wires, that the galvanic needle is in a state fit to receive the return-signal given by the Deal Ball when it reaches the end of its fall.
XIII. Chronometers, Communication of Time, and Operations for Longitude.–
The number of Chronometers now on hand is about sixty, of which sixteen are makers' chronometers on trial. The chronometers are rated daily or weekly; the trial-chronometers are rated in heat and in cold; the abstracts of rates are formed; and the repairs are superintended; as in former years.
The Normal Clock, with its small adjusting apparatus (described in last year's Report), has been in constant use, and has been, found exceedingly convenient. It drops the Greenwich Ball and the Strand Ball, it sends daily signals along several railways, and it maintains in sympathetic movement several clocks, by galvanic currents. Among other clocks thus moved, one is in the Chronometer Room, one is at the Entrance Gate, and one is at the South-Eastern Railway Offices, London Bridge. With the sanction of the Commissioners of Greenwich Hospital, it has lately been arranged by the Rev. George Fisher and myself that two wires shall be swung across the lower part of Greenwich Park, from the top of the Octagon Room of the Royal Observatory to the Observatory of the Hospital Schools, for carrying the galvanic currents which will maintain the movement of a sympathetic clock at the School Observatory.
I alluded, in my last Report, to the erection of a Time-Signal Ball at Deal, to be dropped every day by a galvanic current from the Royal Observatory. The Ball has now been erected by Messrs. Maudslays and Field, and is an admirable specimen of the workmanship of those celebrated engineers. The galvanic connexion with the Royal Observatory (through the telegraph wires of the South-Eastern Railway) is perfect. The automatic changes of wire-communications are so arranged that, when the Ball at Deal has dropped to its lowest point, it sends a signal to Greenwich to acquaint me, not with the time of the beginning of its fall (which cannot be in error), but with the fact that it has really fallen. The Ball has several times been dropped experimentally with perfect success; and some small official and subsidiary arrangements alone are wanting for bringing it into constant use. I can scarcely convey to the Visitors how much I am indebted to the South-Eastern Railway Company and the Electric Telegraph Company, and to their principal Telegraph Officers, Charles V. Walker, Esq., and Latimer Clark, Esq., for the liberality and even the zeal with which they have assisted me in every step of these preparations. Without the cordial aid of Mr. Walker, in particular, it would have been impossible to complete the work. The best line of wires on the Railway has been devoted to this purpose, and the shifting connexions have been modified to diminish the resistance and remove the chances of disturbance as much as possible.
No step has yet been taken for the galvanic determination of the longitude of Oxford Observatory, although I believe that the preparations within that building are now complete.
The determination of the difference of longitude with the Paris Observatory had long been contemplated as one of the important uses of our galvanic connexions. In the last summer and autumn, I recommenced correspondence with Messrs. Arago and Laugier for this object; and one of my letters to M. Arago was addressed to him on the very day of his death. Deeply do I grieve that this operation was not finished in time for him to know the results: not a day, however, had been lost in pressing it forward. It was obviously impossible then to proceed with it; and I considered myself at liberty to take measures in concert with M. Quetelet for our difference of longitude with Brussels. The Submarine and European Telegraph Company, through an unusually protracted operation, gave their warmest assistance. A most able assistant from the Brussels Observatory, M. Bouvy, came to Greenwich, and Mr. Dunkin went to Brussels: when the operation was half finished, the observers returned to their original posts. The signals were continued every night (an hour each night) until three nights' signals had been obtained, accompanied with unexceptionable transits, in each part of the operation; and these alone were retained as available for longitude. Thus, about 3000 effective signals were made, but only 1000 of these were admissible for the fundamental objects of the operation. The result, I need scarcely remark, claims a degree of accuracy to which no preceding determination of longitude could ever pretend. I apprehend that the probable error in the difference of time corresponds to not more than one or two yards upon the earth's surface.
One of the earliest steps taken by M. Le Verrier, after his appointment to the charge of the Observatory of Paris, had reference to the determination of our longitude-difference. All important preliminaries are now arranged, and I trust to be able to report orally to the Visitors the commencement, or probably the conclusion, of this long-desired operation.
The perfection of our galvanic connexion with Edinburgh having been fully established by the operations of last year, I had proposed to use it for the determination of the longitude of a. more distant point. For checking the azimuthal accuracy of our great National Survey, as well as for giving (by interpolation) the error of longitude of every point of our coasts, I had intended to determine with the utmost accuracy the longitude of Lerwick, in Shetland .. I proposed to establish a galvanic connexion with a comparing-observatory on the Granton Pier, and to transmit the time from that point to a selected station in the neighbourhood of Lerwick, by a large number of chronometers carried in the steamboat which plies between Granton and Lerwick. With the sanction of the Admiralty, a grant of money for defraying the expenses was inserted in the Navy Estimates; and other preparations were made. Unfortunately, the demand for chronometers caused by our large naval armament has been so considerable that I cannot reckon on having at my disposal a sufficient number to carry on this operation successfully; and I have, therefore, unwillingly deferred it to a more peaceful time.
XIV. Personal Estab1ishment.–
Mr. Henderson having resigned, and the vacancy having been filled by the appointment of Mr. Charles Todd, formerly supernumerary computer, and lately Assistant at the Cambridge Observatory. The present list of officers is:– … Mr. Todd (succeeding to Mr. Henderson in that responsibility) has the charge of the galvanic apparatus.
XVI. General Remarks.–
The past year has, on the whole, been felt as a laborious one. This has arisen from a cumulation of several perfectly distinct causes. The order of our printing has been disturbed, and this has produced great disarrangement of all our ordinary daily work. The establishment of our galvanic system, and its application to American transits, to public time-signals, and more especially to the longitude-determination, has caused to the establishment in general, and to myself in particular, a great consumption of time. … The American method of transits adds to our labours; but it appears likely to contribute to accuracy, and it will give facilities for the record of the observations made at other Observatories, upon our registering-barrels; and, if these advantages are established by experience, the method must be maintained.
The public dissemination of accurate time brings some trouble; but it is a utilitarian application of the powers of the Observatory so important that it must be continued. The galvanic determination of difference of longitude brings with it a mass of work in negotiations, in preparations, and in calculations; but it produces results of such unimpeachable excellence, and of such value to astronomy and geodesy, that it must in any wise be preserved as part of our system. … All these are additions to the labours of the Observatory as they existed a few years ago, unbalanced by any corresponding subtraction.
The date to which the statements of the Report apply is 1855, May 15, and the interval embraced in its historical portion is that between 1854, May 26, and 1855, May 15.
I. Grounds and Buildings.–
In order to avoid the annoyance which we have several times experienced by being compelled to open the ground for laying down or taking up galvanic wires, I have had several channels constructed of masonry, in the places where wires will usually be required.
V. Astronomical Instruments. –
The Barrel-Apparatus, for the register of transits by punctures produced by galvanic communication, has been in constant use without suffering injury except in the parts exposed to continual friction, which require occasional attention. The method of giving the time-second-signals from the Transit-Clock, which I described in my last Report, is found to be perfectly successful. The insulation of the touch-apparatus has sometimes failed in very damp weather; but, when the sky has cleared, the moistened gutta percha has become dry and the insulation perfect, so speedily that very few transits have been lost.
The rest of the Galvanic Apparatus is, in most respects, in the same state as at the last meeting of the visitors. In the Galvanic Magnet for dropping the Time Signal Ball, it has been found desirable to guard against the risk of permanent magnetism, by causing the apparatus itself to reverse the poles of the battery at every drop of the ball. When arrangements were originally made for exhibiting the London currents upon the Transit-Clock needle, and for sending currents to and through London by the touch-apparatus of the Transit-Circle; in order to avoid disturbing the ground, I so connected the wires by turn-plates that one of the wires of the barrel-apparatus was used for these purposes; but with the increased facilities which I now possess for laying wires, I intend to make the barrel-apparatus-wires entirely independent of the others, preserving, however, the power of' connecting the touch-apparatus with the London and foreign wires.
VII. Reduction of Astronomical Observations. –
The following remarks on the remit of the reductions may not be without interest.
During the whole time of which I have spoken, the galvanic-contact method has been employed for transits, with the exception of a few days, when the galvanic apparatus was out of order. From the clock-errors, I have deduced the personal equations of the observers in our usual way; not by making special experiments, in which I have very little confidence, but by taking the transits as we find them, and discussing them on the supposition that the clock-rate has been very steady; a supposition in the adoption of which we arc amply justified by the comparison of the clock· errors. The result is, that the magnitude of the personal equations in the galvanic-touch-method is not above half of that in the eye-and-car method.
XIII. Chronometers, Communication of Time, and Operations for Longitude. –
The number of Chronometers now on hand is about sixty: twenty of these being on trial for purchase. They are compared, some every day and some every week, and occasionally in extreme temperatures; the repairs of those which belong to the Government are managed; and weekly reports of rates, and monthly reports of repairs, are made to the Admiralty.
The system of Galvanic Normal Clock and Sympathetic Clocks is in the state described in the last year's Report; with this difference only, that the wires to the clock at the Hospital Schools, instead of being suspended across the Park, are carried underground. The clock at the London Bridge Station is made to distribute the galvanic hourly signals to the Electric Telegraph Company's wires and to the different branches of the South-Eastern Railway wires.
The Time-Signal Ball at Deal was brought into regular use at the beginning of the present year. In a short time, however, its action was interrupted, partly by derangement of the apparatus, and partly by the severity of the weather, which froze the sulphuric acid to the state of jelly. I sent an Assistant and workman to put it in order, and since that time it has generally acted very well. Since March 2 there have been three failures; one of these arose from the Ball hanging on the clips, which were not properly oiled, and one from the turning oft· of the current on the Railway line; the cause of the third has not been traced out with certainty. The success or failure of the drop is known immediately at Greenwich; as the Deal Ball, at the termination of its fall, so alters the connexions of wires that a signal is sent to the Observatory. A register is kept in a prescribed form in the Ball-Tower at Deal, and copies of this are sent to the Observatory, leaf by leaf, as soon as they are filled. These cautions I consider to be absolutely necessary for maintaining the regular action of the mechanism under rather difficult circumstances. The whole system is so successful that I have no hesitation in recommending its extension to the Government.
Application has been made to me from one of the important offices of Government, for the galvanic regulation of their clocks. On considering the risks to which various galvanic communications are liable, and the financial necessity for occupying wires as little as possible, I perceived that it was necessary to devise constructions which should satisfy the following conditions. First, that a current sent once a-day should suffice for adjusting the clock, even if it had gone ten or more seconds wrong. Secondly, that an occasional failure of the current should not stop the clock. I have arranged constructions which possess these characters, and the artist (Mr. C. Shepherd) is now engaged in preparing estimates of the expense. I think it likely that this may prove to be the beginning of a very extensive system of clock regulation.
The details of the operation for determining the longitude of Brussels Observatory are published in the Memoirs of the Royal Astronomical Society.
At the last meeting of the Visitors, M. Faye was present at Greenwich, having come as the representative of M. Le Verrier, to conduct the first part of the Transits and Galvanic Signals, by which our difference of longitude with Paris was to be determined. Mr. Dunkin, at the same time, had gone to Paris. After finishing that series of Observations, M. Faye returned to Paris, and Mr. Dunkin to Greenwich, and the second series was completed in a similar manner. The whole number of days of signal-transmission was eighteen, and the whole number of signals transmitted was 2,530. The number of days considered available for longitude, in consequence of' Transits of Stars having been observed at both Observatories, was twelve; and the number of Signals was 1,703. Very great care was taken on both sides, for the adjustments of the instruments. The resulting difference of longitude, 9m.20s.63, is probably very accurate. It is less by nearly 1S of time than that determined in 1825 by Rocket-signals, under the superintendence of Sir John Herschel and Colonel Sabine.
The time occupied by the passage of the galvanic current appears to be 1/12 of a second.
No other operation has been undertaken for determination of longitude.
XIV. Personal Establishment.–
Mr. Henry takes general charge of the Transit-Circle and of Chronometers, Mr. Dunkin of the Altazimuth.;- Mr. Breen has a general supervision of calculation and printing, and controls the supcrnumerary computers; Mr. Ellis and Mr. Criswick are charged with all galvanic adjustments, and with attention to the Barrel-Apparatus for register of transits by galvanic touch.
XV. Extraneous Works. –
The most serious work, not included in the general business of the Observatory, which has partly occupied the personal strength of the Establishment during the last year, is a series of Pendulum Experiments undertaken in the Harton Colliery, for ascertaining the variation of gravity on descending to the bottom of a deep mine. It is not necessary for me to describe at length the laborious but unsuccessful attempts made by two Members of this Board and myself nearly thirty years ago for the same purpose. It will be sufficient to state that, in the last summer and autumn, finding several circumstances favourable for again attempting the experiment, and supported by a grant of money from the Admiralty which defrayed the greater part of the incidental expenses, I borrowed the necessary apparatus from the Royal Society, and sought and obtained personal assistance from the Observatories of Cambridge, Oxford, Durham, and Hed Hill. Two Observers (Messrs. Dunkin and Ellis) were sent from this Observatory. The experiments occupied about a month. The abstraction of so much valuable strength from the establishments which I have mentioned must have been strongly felt; but I trust that it will be recompensed by the understanding that the experiments appear to have been in every point successful, showing beyond doubt that gravity is increased at the depth of 1,260 feet by 1/19000 part. I trust also that this combination may prove a valuable precedent for future associations of the different Observatories of the kingdom, when objects requiring extensive personal organization shall present themselves.
XVI.-General Remarks. –
A fair examination of the statements already made will show how much our real disposable force has been weakened, by accidental circumstances, during the last year. Two Assistants were absent for a month on the Pendulum expedition, and the whole of the extensive calculations which followed were made in the Observatory. One Assistant was employed for some time at Deal, another being at the same time partially occupied in London. The longitude of Paris required the absence of an Assistant for some weeks, and threw a great mass of calculation upon us.
THE Report which I now present to the Visitors applies to the state of the Observatory, on 1856, May 19. The interval between the date of the last Report, 1855, May 15, and that of the present Report, embraces a period of twelve and a half lunations, which is convenient for the exposition of several points in the astronomical history of the Observatory.
I. Grounds and Buildings. –
In order to obtain more room and more convenient accommodation for our galvanic batteries, it has been necessary to occupy the small cellar at the foot of the Octagon Room staircase; and, to bring this into connexion with the rest of the battery basement, a subterranean passage has been made between the basement of the Octagon Room staircase and the basement of the North Dome staircase.
II. Moveable Property. –
No change has been made which is worth mention, beyond the incessant petty alterations of furniture, &c., incidental to a busy office. … There are lent from the Observatory; a journeyman clock to the South Eastern Railway Station, for occasionally keeping up the motion of thc large galvanic clock there (the property of the Royal Observatory) ; a journeyman clock and bar magnet to the Observatory of Kew; …
V. Astronomical Instruments:–
The Barrel Apparatus, for chronographic registration of transits in the American manner, is in good order. To make this theoretically perfect, means are wanted for making the time of rotation practically equal in large arcs and in small arcs (the rotation in large arcs being at present made in the shorter time). I have not yet succeeded in arranging a mechanical contrivance for this purpose.
The Galyanic Apparatus for clock movements remains in the same state as in last year. That for communication of signals has received the following alterations. The clock is employed solely to pull a detent (the same which drops the Time Signal Ball if the Ball is raised); it makes this pull at every hour. The motion of this detent acts in the \yay of relay to complete circuits of independent batteries to the South Eastern Railway (for Deal at 1 o'clock, and for other lines of the South Eastern Railway at other hours), and to Lothbury (for extensive distribution on railways, and for regulating the Post-office clocks, dropping the Strand ball, &c. Probably in no long time other circuits will be completed by the same detent-motion. The entanglement of wires and of the relations of circuits is materially diminished by this alteration. The Motor Clock has been transferred from the Galvanic Register Room to the Ball Lobby.
VII. Reduction of Astronomical Observations. –
The Personal Equations of Transits in the chronographic method of registration, as deduced from the observations of 1855, are (as before) very small. One amounts to 0s.14, and one to 0s.11 ; the largest of the remainder is 0s.05.
XIII. Chronometers, Communications of Time, and Operations for Longitude. –
The number of Chronometers of all kinds now on hand is sixty-five. They are compared with a mean solar clock, daily or weekly, as appears to be necessary. The Chronometers on trial for purchase are sometimes exposed to extreme temperatures. The valuations, repairs, receipts, and issues of Chronometers purchased for or belonging to the Government, are generally managed in the Observatory.
On 1855, December 6, the Time Signal Ball was blown down. An examination of the broken mast revealed the cause of its decay; the ball has now been reinstated in a way which it is hoped will not again expose it to similar accidents.
The Galvanic System of Clocks is in the same state in which it was last year.
The Time Signal Ball at Deal is dropped regularly every day, by the action of the galvanic current from the Royal Observatory, without any material interruption. Where the circumstances of communication are so extremely complicated (for the Deal line is perhaps the most difficult that could have been selected in the kingdom) "there will be occasional failures; and without the active assistance of C. V. Walker, Esq., (Superintendent of Telegraphs of the South Eastern Railway,) they might have been numerous. As it is, the number of failures is very small.
As it appears probable that the system of Time Signal Balls may receive some extension, it is intended (at the first opportunity) to make an alteration in the galvanic communication with the Submarine Company's lines, which will facilitate our connexion with the principal Dockyards.
One of the Galvanic Clocks in the Post Office Department, Lombard Street, is already placed in connexion with the Royal Observatory, and is regulated at noon every day, sending also a signal at a certain minute before noon, to inform me how far it is then wrong, and sending another signal at a certain minute after noon, to assure me of the efficiency of the correction. Other clocks at the General Post Office are nearly prepared for the same regulation, and I expect that the complete system will soon be in action. The difficulties attending a new enterprise of this kind cause to all parties (except the actual workmen) an amount of trouble which cannot be adequately represented by money, and I can only express my thanks to Latimer Clark, Esq., Engineer of the Electric Telegraph Company, for the aid which he has given in a very annoying series of trials and adjustments.
No operations have been undertaken for difference of longitude.
XIV. Personal Establishment. –
Mr. Henry, in the last year, has taken special charge of the Zenith Distances with the Transit Circle, and of Chronometers; My. Dunkin superintends the Altazimuth; Mr. Breen is general inspector of computations and printing, and of the work of the supernumerary computers; Mr. Ellis and Mr. Criswick take charge of the Transits made with the Transit Circle, and of the Galvanic Work.
XV. Extraneous Works. –
In the Pendulum experiments at the Harton Colliery, to which I alluded in my last Report, the temperatures of the upper and lower stations differed about seven degrees. I thought it undesirable to adopt the received tables of correction for this range without further examination; and therefore in the last winter Mr. Dunkin and Mr. Ellis made a series of experiments at the Observatory with the same pendulums which had been used at Harton. They seem to show that Colonel Sabine's correction requires a very small increase, perhaps one twenty-eighth part.
XVI. General Remarks. –
… Lastly, there are employments which connect the scientific observatory with the practical world; the distribution of accurate Time, the improvement of marine Time-keepers, the observations and communications which tend to the advantage of Geography and Navigation, and the study, in a practical sense, of the modifications of Magnetism; a careful attention to these is likely to prove useful to the world, and conducive to the material prosperity of the observatory: and these ought not to be banished from our system.
I HAVE to offer to the Visitors a Report on the condition of the Observatory on 1837, May 23, and on the general history of the Observatory between 1856, May 19, and 1837, May 23.
II. Moveable Property.–
No change of the least importance has been made since the last Visitation. There are lent; a journeyman clock to the South-eastern Railway station; a journeyman clock and hal' magnet to the Kew Observatory; and a copy of Piazzi's Catalogue to the Durham Observatory. Several clocks and other apparatus, the property of the Royal Observatory, as well as four galvanic wires to the London Bridge Station, are employed in the Deal Ball communication, and for other galvanic services.
V. Astronomical Instruments:– The Barrel Apparatus for chronographic record of transits has been in constant good order. To check the occasional tendency of the pendulum to describe an unreasonably large circle (from trifling inequalities in the maintaining power, which it is difficult to suppress entirely), I have mounted a slender spring, so as to produce, when the circle is large, a light friction. As every such friction is accompanied with force directed to the center, it deranges the time of rotation. I have, however, planned a water-resistance which would be free from this· objection, and which I may perhaps adopt in this instrument. A draftsman is at present employed in making plans of the Barrel Apparatus.
The Galvanic Apparatus for clock movements is in the same state as last year, five clocks being in sympathetic movement in the Observatory, one at the Hospital Schools, and one in the North Kent Station at London Bridge. That for signals has received this slight alteration, that the pull of the Time Ball Detent now alters the connexions of four triplets of springs. Of these, one controls the communications with the Electric Telegraph Company's office at Lothbury; by which hourly signals are sent on various railways; the time-balls at the Strand, Cornhill, and Liverpool are dropped; and the Post-office clock in Lombard Street is regulated. A second affects the communications with the South-Eastern Railway Station; by which hourly signals are sent on various lines in Kent, and the Time-Ball at Deal is dropped, and returns its signal to acquaint us with its successful drop. The third and fourth are reserved for the prospective wants of the Royal Dockyards; they communicate with the Admiralty wire of the British Telegraph. The communication with the Post Office clock is remarkable. At 23h. 26m0s of that clock a signal is given to Greenwich, the comparison of which with our clock acquaints us with the error of the Post Office clock. At 0h.0m.0s of the Greenwich clock a signal is sent from Greenwich, which mechanically adjusts the Post Office clock. At 0h.26m.0s of the Post Office clock a second signal is given to Greenwich, by which the efficiency of the adjustment is shown. I am in daily expectation of the extension of this system to three other clocks.
XIII. Chronometers, Communications of Time, and Operations for Longitude. –
The number of chronometers in the chronometer-room is sixty-eight. All are compared with the Mean Solar Clock, which is sympathetic with the Corrected Motor Clock of the Galvanic System: some every day, others once in the week. The chronometers on trial for purchase have, for several years past, been sometimes exposed to extreme temperatures; and lately I have determined to extend this system in a lower degree to the Admiralty chronometers, subjecting all in turns to artificial heat as high as 80° Fahrenheit. The Observatory takes charge of the valuation of chronometers to be purchased by the Government, and of the receipts, repairs, and issues of chronometers belonging to the Government.
The Motor Clock of the galvanic sympathetic system is adjusted every day, after comparison, by means of an auxiliary pendulum, which is put in mechanical connexion for a time with the clock pendulum, and by which the rate of the clock is either accelerated or retarded by 1/100 of its whole value as long as the two pendulums are united. By this clock our own sympathetic connexion is maintained, and time-signals are sent to other places. I am desirous of introducing the system of galvanic connexion for clocks of small dimensions; a system which would frequently be very convenient.
The number of failures of the Time Signal Ball at Deal, dropped by galvanic current from the Royal Observatory, in the course of one year has been nineteen. When it is considered that four connexions must be made on the line before it is fit to receive our current, and that then there must be four contacts at Greenwich and one at Deal, this number of failures will appear very small. Other Time Signal Balls are dropped by currents issued at the same time, at the Strand, Cornhill, and Liverpool; but though I am happy to supply with regularity the currents required for these purposes, I do not hold myself responsible for their success. I have verified experimentally the perfect practicability of dropping a ball at Devonport by a current from Greenwich.
The clock in the Lombard Street Post Office is adjusted and registered with the greatest regularity.
No operations have been undertaken for difference of longitude. But we have made occasional experiments with the relay-instrument in connexion with the Chronographic Transit-Register, as that connexion would be required in the operation of determining longitudes in the American manner.
XIV. Personal Establishment. –
Mr. Dunkin takes charge of the Altazimuth; Mr. Breen attends principally to computations, supernumerary computers' work, and printing; Mr. Ellis and Mr. Criswick control the Meridian Transits, the Galvanic Arrangements, and the Chronometers; and Mr. Lynn superintends the Meridian Zenith Distances.
I PROPOSE to include in this Report a record of the principal transactions in the Royal Observatory between 1857, May 23, and 1858, May 21, and a statement of its condition on 1858, May 21.
I. Grounds and Buildings.–
The passage on the North-side of the East Buildings and the Record-Room, and the approach to the door of the South-East Dome, are protected by a roof of rough glass. The whole of the Astronomical buildings, and the communications between them, and the approach from the entrance gate, are now under dry cover; with the exception of the Galvanic Room, which it will be difficult to connect with the others in the same way, though it would be very desirable to effect it.
II. Moveable Property.–
The words of the last Report to the Visitors might be cited as perfectly applicable to the present time. … we have lent two small clocks, a magnet, and a book. A part of the Observatory property, connected with our galvanic operations, is invested in the South Eastern Railway. ... Our Catalogues of moveable property arc amended from time to time.
V. Astronomical Instruments:–
The Chronographic Barrel Apparatus is in good order. Detailed plans of this mechanism (on which, at the date of the last Report, a draftsman was employed) have been prepared, and are attached to the description which is circulated with the published observations of 1856.
The Galvanic Apparatus, so far as it is included within the Observatory, is in good order. By some parts of this, our system of sympathetic clocks are kept in motion; by other parts, our Time-Ball is dropped, and hourly currents are transmitted to the South-Eastern Railway, and the Lothbury Station of the Electric Telegraph Company, (from which communications are made at 1h to our Time-Ball at Deal, and to other Time-Balls in the Strand, Cornhill, and Liverpool,); by other parts, currents are sent for maintaining the action of a clock at the South-Eastern Railway Station, by which communications are automatically altered; by other parts, we possess the power of giving touch signals from the eye end of the Transit-Circle, to any of the wires of the Electric Telegraph Company, or of the British and Submarine Company. The communications, however, external to the Observatory, have been in a had state. The four wires to London Bridge were injured, as we have reason to believe, by a thunderstorm in the last autumn; and from the circumstance that the injured part is buried in the South-Eastern Railway, and that trains are running at every ten minutes during the day, it has not been possible till lately to open the ground for their examination. I trust that they will now, in the early morning hours, be examined and made good. Our other communication to London, by the Admiralty subterraneous wires crossing Blackheath, has also been in a bad state, but is now made nearly perfect. These faults (as will be stated hereafter) have in some measure impaired the efficiency of our external galvanic action.
XIII. Chronometers, Communications of Time, and Operations for Longitude. –
The number of Chronometers now in the Chronometer-room is one hundred and four. A few of these are on trial for the Brazilian Government. Some of the Chronometers are compared every day, and some only once a week. The standard of reference is a Galvanic Clock, one of the sympathetic series; of which the Motor Clock is every morning adjusted by means of its auxiliary pendulum, to the best Mean Time that the Observatory can supply.
In the last winter, a new Chronometer Oven was prepared, in a form somewhat more convenient than that which we had previously used (and which had been copied from the construction adopted in the Liverpool Observatory). For utilizing space, and at the same time preserving all the essentials of Chronometer-mountings, the simple expedient has been adopted of taking off the lids of the Chronometer-boxes. We are now able to try about forty Chronometers at a time in heat, with mechanical arrangements which I believe are perfectly satisfactory to all parties. Every Chronometer which comes into the Royal Observatory, for whatever purpose, is now rated for some weeks in a temperature of about 80°, and sometimes higher. Some curious neglects of adjustments have been revealed to us, which otherwise might only have puzzled us. I anticipate considerable benefit, not only to the service of the Royal Navy, but also to the habits of Chronometer-makers, from thus regularly directing our attention to the important thermal adjustment. In concluding this subject, it would be wrong to omit the acknowledgment that the careful attention to the subject of temperature is in no small degree due to the example set by Mr. Hartnup at the Liverpool Observatory. The power of carrying out the system in a satisfactory way has been derived from the introduction of gas to the Observatory.
The valuation of Chronometers for purchase by the Government rests (as heretofore) with me. The receipts, repairs, and issues of Government Chronometers, with the preparation of the proper Reports, Abstracts, and Digests, applying to those transactions, are also managed in the Observatory.
The external time-signals are given by the same regulated Motor Clock by which the Chronometer Clock is kept to accurate time.
In spite of the injury to our London Galvanic wires, the currents sent at mean noon every day have had sufficient power to effect the regulation of four Clocks of the General Post Office, by means of an apparatus which I explained- to the Visitors two years ago; and also to exhibit the signals given by those clocks. The appearance here is very curious. Near to 23h26m, 23h28m, 23h32m , and 23h36m, four signals are exhibited which we know to come from four certain clocks, and which, by comparison with our clock, shew the errors of those four clocks. Of the correction effected at noon we see no trace; but very nearly at 0h26m, 0h28m, 0h32m, 0h36m, come four signals, showing the state of the same clocks as corrected. These observations are recorded. Each of the four clocks in question regulates a group of dependent clocks, by local galvanic currents, in a manner nearly similar to that by which our current at noon regulates those four principal clocks, and thus more than thirty clocks are kept very nearly to accurate time. I believe that it is the best instance of mechanical regulation that exists.
The state of the wires, however, has not enabled us to drop the Ball at Deal. The feeble current which arrives there has been used for some months merely as giving a signal, by which an attendant is guided in dropping the Ball by hand. The system has thus lost much of its original dignity; but I trust that under the kind attention of C. V. Walker, Esq., F.R.S., (Telegraph-Superintendant and Engineer of the South-Eastern Railway,) the wires will speedily be restored to their pristine integrity, and that we shall drop the Deal Ball by direct current, as formerly.
Operations have been twice undertaken, with partial success, for the determination of the longitude of Edinburgh. The first time was in the month of November. To avoid the defects of our direct line to Lothbury, I took the route of Blackheath, Admiralty, Strand Office, and Lothbury. For five days we had inexplicable failures, currents being visible, but far too weak for use. On the very last day at our disposal I discovered that the failure was in the Blackheath-Admiralty line, which was totally unfit for sending a distant signal. The wire was subsequently examined and repaired; and in the Easter vacation of Parliament the experiment was repeated. Although there was still an escape on this part of the circuit, which made it desirable for us to avail ourselves of the kindness of the Electric Telegraph Company in lending some very delicate instruments, still we were able to receive and transmit every signal efficiently. During the week devoted to this experiment the weather was so bad that only one evening could be used. In that evening, however, the same series of twenty-two stars were observed at both stations; and as the American method of touch-record of transits of stars over every wire was used (each touch, at whichever end, completing a circuit, which gave action to local relays at both ends, by which local batteries were made to impress signals on chronographic apparatus at both ends), we obtained very good materials for retardation of current and for difference of longitude. The retard is 0s.04 very nearly, and the difference of longitude 12m43s.05, subject to personal equations. Our success in this enterprize is entirely due to the hearty aid rendered by the Electric Telegraph Company, not only by the appropriation to our use of one of the long wires to Edinburgh, and by the loan of their instruments, but also by the cordial assistance of their officers, who, without interfering with our operations, gave their personal attention at both stations to render the apparatus efficient.
XIV. Personal Establishment. –
Mr. Ellis and Mr. Criswick arrange for transits and time-communications of all kinds …
THE Report which I have to lay before the Visitors applies to the proceedings in the Royal Observatory from 1858, May 21, to 1859, May 16, and to the state of the Observatory on the last-mentioned day.
I. Grounds and Buildings. –
The principal want now felt in the buildings is that of a covered passage to the Galvanic Register.
II. Moveable Property.–
There is no remark to be made requiring the Visitors' attention. As stated in the last Report, some small things are here in charge, and some are lent or otherwise placed out of our hands.
V. Astronomical Instruments. –
The Chronographic Barrel Apparatus is in good and efficient order.
The Galvanic Apparatus within the Observatory is in good order. The only addition which has been made is the insertion in the Transit-Clock of another pair of galvanic springs, whose contact is produced by the same 60-tooth wheel which produces the contacts of the original pair of springs that make the circuit for seconds'-puncture on the Chronographic Barrel. The purpose of the new circuit is to regulate one of the clocks and to give motion to another, which are used in connexion with the new South-East Equatoreal. As one of the teeth of the 60-tooth wheel is cut away (to mark the commencements of minutes on the Chronographic Barrel), there are sent in fact only 59 currents in every minute; and this requires a singular construction in one of the South-East Equatoreal Clocks, to be described hereafter.
In regard to external Galvanic Connexions, the wires of the South-Eastern Railway Viaduct have been thoroughly repaired, including those of the Royal Observatory; and our communication with London by that course is now good. I have not had occasion to examine the state of communication by the Admiralty Blackheath wire.
The new South-East Equatoreal is now far advanced … The communication of time is made by a small clock with 10-inch pendulum beating seconds, near the fixed microscope of the hour-circle, and by a galvanic chronometer carried by the eye-end of the telescope; but these clocks do not give independent times: the wire of a galvanic battery, whose circuit is completed at 59 seconds of every minute of the transit-clock, is carried through a coil into which swings a bar-magnet carried by the 10-inch pendulum, and is also carried through the coils of the galvanic chronometer, (being led from the fixed support to the polar frame by means of insulated springs on the fixed support, touching insulated rings on the polar frame, and being then led in a similar manner to the telescope,) and thus the 10-inch clock is regulated, and the chronometer is moved, in exact accordance with the transit-clock. The seconds' wheel of the chronometer has only 59 teeth, and the seconds' dial has only 59 divisions, one of which counts for the two successive seconds (28 and 29): this is necessary in consequence of the loss of one current per minute in the transit-clock, as before remarked. In the 10-inch clock, which is merely regulated by the current on the principle introduced by Mr. R. L. Jones, there is no such anomaly.
Another pair of galvanic wires is brought, by insulated rings and springs, to a touch-piece at the eye-end of the telescope: these wires are connected with the pricker of the Chronographic Barrel, so that times may be registered on the same sheets as the times of observations with the Transit-Circle and the Altazimuth.
The clock-movement of the hour-circle is effected essentially by the same mechanism as that which I introduced at Liverpool. By transferring a water supply from a lower to a higher level, I have obtained a fall for driving a reaction machine (Barker's mill), revolving four times in a second. This, acting through two worms, drives the hour-circle. For its regulation, it gives motion to an axis revolving in two seconds, which acts upon a conical pendulum (carried by two pairs of springs that do the duty of a universal joint), by the remarkable contrivance called' Sieman's Chronometric Governor, of which the effect is that, if there is a tendency to acceleration, the throttle-valve of the water-pipe is immediately contracted. It is necessary that the pendulum suffer a retarding force, which ought to be strictly tangential; to effect this, I have so connected a small spade with the rotatory apparatus, that the pendulum by enlarging its cone dips the spade into a trough of water. I anticipate from this a very smooth and uniform motion.
XIII. Chronometers, Communications of Time, &c. – The number of Chronometers now in the Chronometer-room is 129. All are compared, daily or weekly, with a Galvanic Clock that is sympathetic with the Motor Clock, which is adjusted most accurately every day, to Greenwich Mean Solar Time. This is the same Clock which drops the Time Ball and gives signals to London and Deal.
The new Chronometer Oven has been in perpetual use, and numerous faults of adjustment which had escaped the notice of chronometer-makers have been detected[.] I think it probable that we must soon increase the dimensions of the Oven.
The business of valuation and repairs of Chronometers, and of their receipts and issues, rests, as heretofore, with me.
The Post Office Clocks are duly regulated, and the Time Ball at Deal is dropped by direct current, as formerly.
I have called the attention of the Government to the advantage of daily time-signals at Portsmouth and Devonport. Another exhibition of signals also, of a more extensive kind, has been proposed. It was first suggested, I believe, by the Board of Trade, that a signal should be exhibited every hour at one of the principal headlands of our southern coast, for the benefit of ships passing down the Channel; and in the first instance the Lizard Point was named. It appeared to me that the Start Point would be preferable; and with this modification, after having examined the locality, I sub-mitted a detailed plan to the Admiralty. Considerations unconnected with the abstract value of the scheme induced the Lords Commissioners of the Admiralty to defer it for the present; but the matter will be kept in view, for further consideration.
XIV. Personal Establishment. –
Mr. Ellis and Mr. Criswick have under their care the matters which concern time, chronometers, galvanic operations, and external time-signals.
THE rule which I have adopted in several past years, of presenting to the Visitors a Report applying to a period of 12½ lunar months, appears so convenient that I shall retain it on the present occasion. I proceed therefore to lay before the Visitors a Report on proceedings in the Observatory from 1859, May 16, to 1860, May 20, and on the state of the Observatory on 1860, May 20. The usual order will be followed.
I. Buildings and Grounds .–
Upon the roof of the Octagon Room is planted a pole (erected, at my request, by the London District Telegraph Company) for carrying the open-air telegraph wires, which swing from this point to a similar pole erected on the roof of a house in George Street, far beyond the Park Wall. I shall allude hereafter to the necessity of adopting this system for our galvanic communication.
The want of a covered passage to the Chronographic Room, to which I have before alluded, is still occasionally felt. It will not, however, be easy to supply it.
V. Astronomical Instruments: –
The Chronographic Barrel Apparatus, though generally doing its duty very well, has not lately been quite so steady in its motions during fractional parts of a second as I could wish. The active cause of this unsteadiness is some irregularity in the communication of force through the train of wheels: the want of suppression of its effects arises from the want of sufficient moment of inertia in the fly. I propose to add a multiplying wheel, by which the fly, instead of revolving once in two seconds as at present, will be made to revolve several times in one second. –The mere resistance of the atmosphere, also, is found to be scarcely sufficient to determine the conical angle of the pendulum with sufficient accuracy (an adjustment which requires attention, because the effect of a given angle of swing on the rate of the pendulum is six times as great for a conical pendulum as for a plane pendulum). I contemplate the introduction of an apparatus, on a lighter scale, similar to that which I have introduced with perfect success in the water-clock of the Great Equatoreal; where the enlargement of the pendulum's arc dips a plane resisting piece into water, and thus produces a resistance which is purely tangential, without any of the centripetal force which accompanies frictional resistance, however the friction may be applied. This principle, in the water-clock of the Great Equatoreal, is found to produce astronomical accuracy of motion. – The galvanic wires which convey the currents that give the observation·punctures on the Barrel are now connected with the touch-piece on the eye· end of telescope of Great Equatoreal; so that the observation-punctures are now made by the same pricker from contacts at either of the three instruments, Transit-Circle, Altazimuth, or Equatoreal.
The Galvanic Apparatus within the Observatory has received the following addition. The visitors will remember that a pair of galvanic springs was mounted in the Transit-Clock, giving 59 contacts in 60 seconds, by which the motion of a 10·inch clock in the South-Eastern Dome is regulated to sympathy, and by which the movement of a Chronometer carried by the eye-end of the Great Equatoreal is absolutely maintained, (a. 59-tooth wheel, and a 59-division dial, one special division counting for two seconds, being required for this Chronometer). The same current is now made to pass also through a similar Chronometer in the Computing Room, which is thus maintained in sympathy with the Transit-Clock. There is also, placed near the Chronometer just mentioned, another small clock which, by a special pair of wires from the Solar Motor Clock, and a portion of the Clock Battery, is kept in sympathy with the Motor Clock. And near to these is a commutator for changing the direction of the current of an appropriated battery. The use of this battery is to produce attraction or repulsion of a galvanic coil (without core) which is fixed within the case of the Motor Clock, upon one pole of a bar-magnet, which is carried by the pendulum-rod. and is parallel to the pendulum-rod. The pole of the bar-magnet swings immediately above the pole of the galvanic coil, so as to receive the greatest attraction or repulsion which the coil can give: when the force is attractive, the force of gravity on the pendulum is augmented, and the clock is made to gain; when the force is repulsive. the clock is made to lose. The Galvanic Superintendent has, therefore upon his desk, a representative of the Transit-Clock and a representative of the Motor Clock, which he can compare; and when, by this comparison, and the necessary reduction, he has ascertained the error of the Motor Clock, he has merely to turn the commutator-handle, and to let it remain in that position for a certain time, in order to correct the small error of the Motor Clock. By using a battery of low power, the correction of the Motor Clock may be made very gradual, and this is sometimes desirable, for the following reason: It is probable that we may soon make it our business to regulate, by action at every second on the pendulum, clocks at the London Bridge Terminus, at the Office of the London District Telegraph Company, at the Chronometer Makers' Institution at Clerkenwell, &c. As the force transmitted to these distances is small, the rates of the clocks without adjustment must be very near together, say within 1/1000 part. If then we had attempted to correct our Motor Clock by the old process, which changed its rate for a time by 1/100 part, its action upon the distant clock would have failed to draw that clock's pendulum into sympathy with its own, the difference of 1/100 in the rates for that time being too wide. But by the new process we can, with the utmost personal convenience, affect the rate by not more than 1/2000 or 1/3000 part, and the regulation of the distant clock will then never fail.
Our external galvanic communication has received a very important change. We had found for some time that our two underground wires leading to the Blackheath Gate of the Park, and there adapted to communicate either with one of the Admiralty wires (to the Admiralty, or to Woolwich, Chatham, Sheerness, Deal,) or with one of the Submarine Company's wires (to the London Office, or to Calais or Ostend,) had become practically useless. One of the four underground wires crossing Blackheath to the Lewisham Station of the North Kent Railway (there communicating by the London Bridge Station with Lothbury and with Deal,) had shown signs of decay, but the others were very good; but about the month of August last year the whole of the four wires failed. We have taken up parts and replaced them by new wire, but apparently the whole of the gutta percha has perished. No special fault has been found, but every yard is faulty. I determined after this to trust no more to underground wires; and having received the permission of the Right Honourable the First Commissioner of Parks and Public Works, to extend wires at sufficient elevation above the Park; and having been met in my application to the London District Telegraph Company by the most liberal offer on their part; I have stretched seven wires in the open air from the top of the Octagon Room to the top of a house in George Street. From this point the wires are carried on in a similar manner to the following destinations :– One is the property of the London District Telegraph Company. Four are led to the Railway Station in Greenwich, whence, under the care of Charles V. Walker, Esq., they are continued on poles till they rejoin the continuation of the former North Kent lines at the railway junction. (Mr. Walker is preparing arrangements for placing the wires in open air all the way to the London Bridge Station.) Two are led along the poles of the London District Telegraph Company to Deptford Broadway, where they meet the lines of the Submarine Company, and where they will communicate by turnplate either with the Admiralty line or with the Submarine line, as formerly at the Blackheath Gate of Greenwich Park.
The South-East Equatoreal may now be considered in a state for use. … the clock-work acting on the hour-circle, the water-power and reaction-machine which drive it, the· pendulum and chronometric-governor which regulate it (the enlargement of the pendulum-arc dipping a revolving spade into an annular trough of water); also, the leading of gas to all parts of the instrument, and even to the eye-end of the telescope, and the leading of galvanic communication to the 10-inch clock, to the chronometer on the eye-end of the telescope, and to the contact-springs there. … The following adjustments could not be made until the clock-work was in perfect efficiency. I will shortly speak of it; and, supposing it effective, will now state the order of adjustments of the instrument following the first, already described. … The reaction-machine of the clock-work at first gave some trouble. I do not doubt that, with due modification of adjustments, the same machine may be adapted to varying heads of water; but, after repeated trials of pressure from the water-mains and pressure from a fixed cistern supplied by the water-mains, I found the use of the fixed t will be remarked that the uniformity of action of' the clock-work depends, in the last instance, upon the truth of the large 2-minute worm or screw, which acts in the racked teeth of the hour-circle. Many months ago, I had requested Messrs. Ransomes to point out to me the screw-cutting machine which they intended to use for the generation of this worm. I then had a brass cylinder placed in the machine, and had lines scratched upon it by the action of the machine, representing the spiral of the worm, and I had a frame expressly prepared to carry a micrometer-microscope for measures of the longitudinal ordinate of the spiral. After numerical analysis of these measures, I was well satisfied with the accuracy of the machine. I have since examined the appearance of a star under the wire, but have seen nothing like a disturbance with a period of two minutes. For cutting each tooth of the hour-circle, the circle was placed in position by microscopic reference to Mr. Simms' graduations.
XIII. Chronometers, Communications of Time, &c. –
In consequence of an unusual demand for Chronometers by the Admiralty, the number of chronometers on daily rating during the past spring has been great beyond all precedent. The largest number in our hands at one time was about 210. The number at present on hand is about 140. A few of these are compared only once a week, but the far greater part are compared every day. The standard of comparison is the Motor Clock, which gives general time-signals, drives the Sympathetic Clocks, and drops the Time-Signal-Balls at Greenwich, London, and Deal.
The Chronometer-Oven has been much enlarged, and (by a peculiar method of arrangement) about forty chronometers can now be placed in the Oven, and can be compared with the clock, without removal of any part of their boxes. All chronometers are now, as matter of routine, rated, during a part of their stay here, at an elevated temperature.
The estimation of the merits of chronometers offered to the Government on competition or for purchase is made by me, and the superintendance of repairs of Government chronometers rests with me. In general, all Government chronometers pass through the Observatory before being issued to the Royal Navy.
Although our galvanic currents to Deal have been, during the almost complete failure of our underground galvanic wires, exceedingly feeble, still there has always been a signal sufficient to enable the Superintendant at Deal to drop the Time·Ball with accuracy. The regulation of the Post Office Clocks has, however, failed almost completely. I expect that all will shortly he restored to their original perfection.
No further step has been taken by the Admiralty for the exhibition of Daily Time-Signals at Portsmouth and Devonport, or of Hourly Time-Signals at the Start Point. All these schemes are, in my opinion, important; and I propose, when opportunity presents itself, again to urge them.
No measures have been taken in the last year for further determination of longitudes (as referred to Greenwich) in Britain or on the Continent. Our wire-communications however now enable us to reach (I believe) every point. Considering how small is the expence of such determinations; and how great is their value, either as furnishing an independent basis of comparison with the Trigonometrical Survey, or as giving the elements of measure of an Arc of Parallel; it appears desirable that they should not be allowed to escape our attention. I lately circulated among the Visitors an exposition of Mr. Struve's views of the steps, in this direction, which it appeared desirable to take in Britain for the promotion of European Geodesy; and I ask leave to submit them to the special attention of the Visitors.
XIV. Personal Establishment.
– Mr. Ellis and Mr. Criswick principally taking charge of time and galvanism in all their branches; …
XVI. General Remarks. –
If the time-signals at Portsmouth, Devonport, and the Start, be brought into action, the superintendance of these will produce additional office-work, which, however, may be provided when the necessity for it shall arrive
ADDRESS OF THE ASTRONOMER ROYAL TO THE MEMBERS OF, THE BOARD OF VISITORS OF THE ROYAL OBSERVATORY.
IT is known to several of the Visitors that, in the autumn of 1857, Mr. Struve visited this country on his way from France. His chief business had been to visit the Central Offices of Survey of the principal Continental States, and to endeavour to make arrangements for effectually carrying out the observations (where needed) and the computations, for exhibiting the comparison of measure with theory in one or more extensive arcs of parallel. In prosecution of this purpose, Mr. Struve had been permitted personally to lay his views before the Emperor of the French. Mr. Struve had examined the state of calculations in the British Survey Office (at that time unpublished), and was preparing to take further steps, when he was struck with the serious illness from which he has yet but imperfectly recovered.
In the want of reports from Mr. Struve, I have been unable to take any distinct step for furthering his proposals. But I have lately ascertained from Mr. Otto Struve that the measures which Mr. Struve was desirous to suggest, as regards the proceedings in the British Survey, are mainly the following :-
1. That the junction between the British and the French or Belgian triangles should; if necessary, be repeated.
2. That a new determination of the longitude of Valentia by the galvanic telegraph might be recommended; especially as, on the former occasion, personal equations were determined only at the end of the operations, and observers were not interchanged.
3. That the longitude of the extreme eastern station of the British triangles should be fixed by galvanic telegraph.
4. A scrupulous examination of the principal triangles might be made, and perhaps the measures might be repeated wherever that examination should indicate a weakness.
5. If necessary, a new comparison of the units of measure employed on the different base lines might be made.
And I now submit these suggestions of Mr. Struve to the consideration of the Visitors.
The points in which the Royal Observatory is practically concerned are Nos. 2 and 3 alone. In considering these, it might also be well to take into consideration whether the determination of the astronomical longitude of other points of the British Triangulation should be recommended.
FOR convenience, I have this year included in the period to which my Annual Report to the Board of Visitors applies, 12 complete lunations (instead of 12½ as in several late years). The Report which I have now the honour to offer exhibits generally the state of the Observatory on 1861, May 10, and the proceedings in the Observatory from 1860, May 20, to that date.
1. Buildings and Grounds. –
A change has been made in the direction of the galvanic wires, suspended in the open air, which lead from the top of the Octagon Room to the top of a house in George Street. These wires, as originally placed, passed over a part of the dwelling of a resident on Croom's Hill. The owner naturally desired to secure himself against intrusion on his rights as proprietor, but expressed the strongest wish to aid in promoting the objects of the Observatory. With this feeling, I did not anticipate the least difficulty in making a satisfactory arrangement. Unfortunately, the business was placed in the hands of solicitors; and it was soon found that all accommodation was hopeless. A lease was offered, but such conditions were attached to it that the London District Telegraph Company declined to take it, that I could not advise the Admiralty to take it, and that I was unwilling to take it on my personal responsibility.
Accordingly, the wires were removed, and a new course was adopted for them, by which, in three steps instead of one, we arrive at the same point which was reached before.
I anticipate that in no very long time considerable extension of our buildings will be found necessary, … Yet, with increase of computations, we want more room for computers; with our greatly increased business of Chronometers and Time-Distribution, we are in want of a nearly separate series of rooms for the Time-Department; we want rooms for … Whatever plan may be ultimately proposed, I presume on the feeling of the Visitors, that the Observatory Hill must never be abandoned as the place where the fundamental Meridional Observations are to be made.
V. Astronomical Instruments: –
The Chronographic Barrel Apparatus has received the changes which I suggested in my last Report. The fly is made to revolve five times in one second; and the maintaining power upon the pendulum is resisted by a spade rotating with the pendulum, which the increase of the diameter of the pendulum-cone causes to dip into an annular trough of water. As the apparatus was not adapted in its original plan for this addition, a little trouble was experienced in fitting the spade with a proper counterpoise. The movement is now extremely uniform, and very accurate. The only remaining chance of inaccuracy in the subdivision of seconds of time by the barrel-movement arises from the use of toothed wheels in the communication of motion from the clock to the barrel.
The Galvanic Apparatus has received no change, except that we have connected with the wires of the sympathetic system an oscillating magnet, whose oscillations complete at every second the contacts of several pairs of springs, and thus enable us to send currents every second in several different directions. The method of adjusting the Motor-clock by galvanic action, in the manner described in the last Report, is now in daily use, and is found very efficient and convenient.
Our external Galvanic communications are in the best possible order; as far as London Bridge, for the various connexions there required (to the South-Eastern Railway and Deal, and to the Electric Telegraph Company); and as far as Deptford, (for connexion with the Magnetic and Submarine Company's wires, and with the Admiralty wires).
The South-East Equatoreal is thoroughly efficient for ordinary observations … The water-clock is now brought so completely under command that we use the direct power of the water from the water-mains, under any variation of pressure. The quantity of water required is thus much diminished. In the late severe winter, the water-main of the Observatory (which is in a very bad position and bad state) was frozen, and the water used for regulating the pendulum movement was also frozen; and the clock could not be used for a few weeks. I trust however that the pipes will be laid in a better state, and that the winters will not often be so severe; and I attach no importance to this hindrance.
XIII. Chronometers, Communications of Time, Longitudes, &c. –
The demand for Chronometers for the service of the Royal Navy has continued, and in consequence we have been very much pressed with the business of all kinds attending their trials and the usual care of Navy Chronometers. The number of chronometers on hand has been as high as 220: it is now 120.
The chronometers are compared with the Motor Clock, which is every day adjusted to exact Mean Solar Time.
By use of the Chronometer Oven, to which I have formerly alluded, we have been able to give great attention to the compensation. I have reason to think that we are producing a most beneficial effect on the manufacture and adjustment of chronometers in general.
The decision on the merits of Chronometers tried for purchase by the Government, and the superintendance of repairs of Government Chronometers, still rest with me.
Since our open-air galvanic wires have been established, our communications with London and Deal have been perfect. The ball at Deal is regularly dropped by our current (as are also other balls, for which I am not responsible officially), and the regulation of the Post-Office Clocks is complete. Time signals are sent daily to almost every part of England.
In galvanic arrangements, I constantly bear in mind the probable exhibition of Daily Time-Signals at Portsmouth and Devonport, and of Hourly Time-Signals at the Start Point. These practical measures have so close a connexion with that subject for whose promotion the Observatory was mainly established, namely Nautical Astronomy, that I may perhaps with propriety ask an expression of the Visitors' opinion on their proposal.
No steps have been taken to determine the galvanic longitude of Lowestoft or of Valentia; the incessant employment of our whole personal force having rendered it impracticable. But the authority of the Treasury has been received, and active steps have been taken by Sir Henry James, for repeating the junction between England and Belgium; and when this shall be done, the British arcs to which I allude cannot be much longer delayed.
XIV. Personal Establishment. –
Mr. Ellis and Mr. Criswick [have charge] of time operations and galvanism; …
THE interval between 1861, May 10, the date of my last Report to the Board of Visitors, and 1862, May 13, includes the convenient period of 12½ lunations. I have, therefore, adopted 1862, May 13, as epoch for the Report which I have the honour now to offer to the Board.
I. Buildings and Grounds. –
As the pressure of the large number of Computers in the ordinary Computing Room began to be felt as a severe inconvenience, I have had the Middle Room of the S.E. Dome fitted up with desks, &c., and the Supernumerary Computers under their Superintendent (Mr. Lynn) are now located there. I have thus been enabled to assign a larger portion of the Computing Room to the Superintendent of Chronometers and Galvanic Time Communications (Mr. Ellis); and nearly the whole of the apparatus of Galvanic Chronometers, Clock Regulators, and Galvanometers, is now collected there.
The water pipe, from the large main of the Kent Waterworks Company on Blackheath (which is always charged and under heavy pressure), to the Observatory, has been entirely relaid with tubes of 3 inches internal diameter.
II. Moveable Property. –
… the principal articles of our property not now within our walls, are the clocks, &c. connected with the transmission of time-signals to Deal.
V. Astronomical Instruments: –
The steel-work of the Transit-Clock (which is almost buried in the South Collimator Pier) had been found extremely liable to rust; but holes have been made through those parts of the Pier which encase the clock, permitting a much more free ventilation of the clock than it formerly received: and the rusting seems to have been in great measure prevented.
The Chronographic Barrel Apparatus continues in the excellent order which was described in the last Report. Some slight changes of rate are possibly due to error of compensation for thermal changes. As the pendulum-suspension and the wheel-mechanism are not carried by the same foundation, a trifling error of adjustment sometimes occurs, which is easily remedied by use of the adjustment-screws.
A small change has been made in the Galvanic Apparatus by which hourly signals are given to external offices, in order to remedy two inconveniences. One was, that the transmission of external signals formerly depended on the movement of the Ball-Detent; and erroneous signals have sometimes been given by mere manual mismanagement of that Detent. The other was, that it appeared probable that we might be requested to give hourly signals on several different lines, for which our former apparatus was not competent. A relay-apparatus has therefore been fitted up in the Computing Room, completing six circuits at every hour of the Motor Clock, without reference to the Ball-Detent.
A delicate Galvanometer, the property of C. V. Walker, Esq., has been mounted in the Computing Room, with intention of ascertaining whether spontaneous Earth-Currents are exhibited by a wire whose ends are connected with earth at London and at Greenwich. Hitherto, it has failed entirely for its legitimate purpose, although it has exhibited great sensitiveness to other currents, induced by signal currents on wires parallel to it, or reflected from wires whose earth-connexion is near to its earth-connexion.
XIII. Chronometers, Communications of Time, Longitudes, &c.–
The number of chronometers on hand now and for some time past is about 160: of these 100 are compared every day, the others being compared once a week. The standard of comparison is a clock, sympathetic with the Motor Clock, which is adjusted to accurate Mean Solar Time. Every chronometer, whether the property of the Government or a maker's chronometer on competitive trial or trial for purchase, is tried in heat in. the Chronometer Oven.
The Reports on the comparative merits of chronometers on trial are furnished to the Admiralty by me; and the management of repairs of chronometers generally is referred to me.
Our galvanic communication with Deal, by which the Time-Signal-Ball at that port is dropped every day, has been uninterrupted except by accidental failure of adjustment of the Clock at London Bridge, which changes the connexions of wires. The regulation of the Post-Office-Clocks is effective.
I have alluded, in the two last Reports, to the steps necessary, on the English side, for completing the great Arc of Parallel from Valentia to the Volga. The Russian portion of the work is far advanced, and will be finished (it is understood) in the coming summer. The improved geodetic junction between Britain and Belgium has been completed several months ago by Sir Henry James. It appeared to me therefore that the repetition of the measure of astronomical longitude between Greenwich and Valentia could be no longer delayed; and I have made arrangements, with the co-operation of Sir Henry James, and with the most liberal assistance of the Magnetic Telegraph Company, for the early completion of this work. Two Assistants of the Royal Observatory (Mr. Dunkin and Mr. Criswick) will at once proceed to Valentia, for the determination of local time and the management of galvanic signals. The Board of Admiralty have supplied funds to meet the contingent expenses. Some of the requisite instruments are lent by the Royal Astronomical Society and by Mr. Simms.
I have alluded, in former Reports, to the exhibition of Daily Time Signals at Portsmouth and Devonport, and of Hourly Time Signals at the Start Point, by means of galvanic currents originating at this Observatory, as matters which appear to merit the consideration of the Board of Visitors and the active care of the Astronomer Royal, and I now ask leave to press the subject of Hourly Time Signals at the Start Point on the attention of the Board, and to submit the advantage of their addressing the Board of Admiralty upon it. The great majority of outward-bound ships pass within sight of the Start, and, if an hourly signal were exhibited, would have the means of regulating their chronometers at a most critical part of their voyage. The plan of the entire system of operations is completely arranged. The estimated expense of outfit is 2,017 [pounds] l., and the estimated annual expense is 326 [pounds] l.; both liable to some uncertainty. but sufficiently exact to show that the outlay is inconsiderable in comparison with the advantages which might be expected from it. I know no direction of the powers of the Observatory which would tend so energetically to carry out the great object of its establishment, "the finding out the so much desired Longitude at Sea."
XIV. Personal Establishment. –
The meridional and altazimuth observations are principally divided between Mr. Dunkin, Mr. Ellis, Mr. Criswick, and Mr. Carpenter (the aid of supernumeraries being, under extraordinary pressures, sometimes called in); the first of these gentlemen having the special care of the Altazimuth, the second and third conducting the business of the time-communications, galvanism, and chronometers; …
XVI. General Remarks. –
I look forward to a season of most unusual pressure upon the computing powers of the Observatory, and to a consequent retardation of the state of reductions. The employment of two able Assistants at Valentia, and of two computers on the Seven-Year Catalogue, will interfere much with the regularity of routine calculations …
THE Report, which I had the honour last year to submit to the Board of Visitors, brought up the history of the Royal Observatory to 1862, May 13th. In the Report now offered, I propose to continue that history to 1863, May 17th.
V. Astronomical Instruments: –
The Transit-Clock, the Chronograph, and the Reflex Zenith-Tube, are in good order, requiring no special notice.
The Altazimuth is in good order. It has lately been subjected to a special examination, for the following reason. In the operations for the determination of the longitude of Valencia (to which further allusion will be made). it was found that a small Altazimuth used at Valencia gave the zenith-distances constantly too great. …
The Galvanic Signal-Apparatus is in good order; no change has been made in it.
XIII. Chronometers, Communications of Time, Longitudes, &c.–
The number of Chronometers on hand at this time is 132; of these, 82 are compared with a standard clock every day, and the others are compared on one day in every week. The standard clock is one of a series of galvanic clocks whose movements are necessarily synchronous with that of the Motor Clock; which is accurately adjusted to Mean Solar Time by means of a galvanic action upon its pendulum, that can be used for any arbitrary length of time to accelerate or retard the clock by slow degrees during that time. Every chronometer, whatever be the reason of its lodgment at the Royal Observatory, is tried during some part of its stay in the heated Chronometer Oven.
When it is necessary to decide on the merits of chronometers, either as affecting their price for purchase, or as deciding their place in the published Order of Merit, the decision is made by me. The repairs of Chronometers the property of the Government are entirely managed by me.
The drop of the Time-Signal-Ball at Deal, by a galvanic current from this Observatory which is automatically given by the corrected Motor Clock, is perfectly efficient, no failures occurring except from the defects of adjustment of the Clock at the London Bridge Station which changes the connexions of wires. Time-Signals are sent daily along the principal lines of railway, the most distant points (I believe) being Glasgow and Cardiff. I have also heard that the companies, through whose offices the wires pass, have begun to distribute branch signals to private factories.
The clocks of the General Post Office are connected as formerly with the Observatory, each of four clocks being adjusted by current from our Motor Clock once every day, and reporting itself to us twice every day. The clock of Westminster Palace has also been brought into connexion, the attendant receiving a signal from us once every hour, and the clock reporting its state to us twice every day. As far as I have yet observed, the rate of this clock may be considered certain to much less than one second per week.
The various operations, connected with Chronometers and Galvanic Signals, including the Chronograph, occupy pretty fully the office-time of two assistants and one computer.
The operations for the redetermination of the longitude of Valencia in Ireland were effected shortly after the last Visitation of the Royal Observatory. The distance (nearly 800 miles by the indirect course of the wires) was not too great for very good exhibition of galvanic signals when the air was not very damp. The principal trouble in the reductions arose from the circumstance. that the small altazimuth used at
Valencia for the determination of local time, from some peculiarity whose cause I have not been able to trace, gave all zenith-distances too great. The observations, however, were so arranged that this leaves no uncertainty in the result. The concluded longitude agrees almost exactly with that determined by the transmission of chronometers in 1844; and entitles us to believe that the longitudes of Kingstown and Liverpool, steps in the chronometer-conveyance, were determined with equal accuracy.
The proposal for the establishment of Time-Signals on the Start Point, introduced by my last Report to the notice of the Visitors, and by them recommended to the attention of His Grace the First Lord of the Admiralty, has been, as I understand, under the consideration of the Government; and some communication on that subject will probably be made to the Board of Visitors.
XIV. Personal Establishment. –
The positions of First and Confidential Assistant, of Superintendant of Altazimuth, of Superintendant of Time-Communications and Chronometers, and of Superintendant of Equatoreal, are held (as at the last Report), by Mr. Edward James Stone, M.A., Fellow of Queens' College, Cambridge, Mr. Dunkin, Mr. Ellis assisted by Mr. Criswick, and Mr. Carpenter.
XVI. General Remarks. –
In the last Report, I did by anticipation solicit the indulgence of the Visitors for anything that might be considered as shortcomings in the Reductions of the year then beginning. From the present Report it will appear that my fears have been in some degree realized. Every part of our Reductions is somewhat (though not very much) in arrear. This is sufficiently explained by the observations and computations of the Valencia Longitude and the Parallax of Mars; the computations of Seven-Year Catalogue and Magnetic Reductions; and the superintendance, by a skilled assistant, of the computation of Solar Movement.
IT has been my rule, in framing my Reports to the Board of Visitors for several years past, to adapt them to periods bounded at the beginning and at the end either by the beginning or by the middle of a lunation. The Report which I have the honour now to place before the Board applies to the period of twelve and-a-half lunations, from 1863, May 17, to 1864, May 20.
I. Buildings and Grounds. –
Two piers have been built in the Front Court for the support of instruments which I expect Mr. Otto Struve to bring, to be used in observations connected with the Great Arc of Parallel. It was necessary to dig to the depth of 12 feet, to obtain a satisfactory foundation for the piers. A portable observatory is to be erected over them in some part of the approaching summer.
In a very heavy squall which occurred in the gale of December 2 of last year, the stay of the lofty iron pillar outside of the Park Rails, which carried our telegraph-wires, gave way, and the pillar and the whole system of wires fell. By permission of the Department of Her Majesty's Parks and Public Buildings, I was enabled to select a new position within the Park, and thus to attach the wires to a much shorter wooden mast. On the last day of the year, communication was again made perfect.
V. Astronomical Instruments: –
The Transit-Clock (lately cleaned) is in good order. To enable us to use another clock by the chronographic method when the transit-clock is temporarily dismounted, I have had seconds-contact-springs inserted in the North Dome Arnold.
The Apparatus of all kinds for Galvanic Signals is in good order. The Motor Clock has been lately cleaned, with much attention to the maintaining-mechanism, and to the galvanic-contact-surfaces: ebonite has been substituted for ivory in some of the insulating parts; and, in order to diminish the mechanical interference with the motion of the pendulum, two pairs of pendulum-contact-springs have been removed, their circuits being completed by a multiple relay, which is worked by the springs that are left.
XIII. Chronometers, Communications of Time, Longitudes, &c. – The number of chronometers on hand at the date of this Report is 168; of these, 101 are the property of Government, and 67 are on the Annual Competitive Trial. The whole of the latter and a portion of the former are compared every clay with one of the galvanic clocks, sympathetic with the Normal Mean-Time-Clock; the remainder are compared with it once every week. Every Chronometer is tried for some weeks in the heat of the Chronometer Oven.
All decisions on the merits of chronometers offered to the Government for purchase, and on the merits of chronometers rated in the Annual Competitive Trial, are referred to me; and the repairs of chronometers belonging to the Government are effected entirely through me.
The system of galvanic clocks (containing among others the Normal Clock, the Chronometer Clock, and the large clock at the Entrance Gate), are all simultaneously adjusted to time by the use, when required, of a galvanic force, which may be kept in action during any arbitrary time, to accelerate or retard the vibrations of the pendulum of the Normal Clock. Another common clock has lately been fitted with contact springs, to enable it to give the currents at every second when the Normal Clock is for a time disabled.
The Time-Signal-Ball at Deal is dropped daily by a galvanic current automatically given by the Normal Clock; and from the first., very few failures have arisen from defect in the Observatory Apparatus. Failures have usually arisen (and, in the late disturbed state of the South Eastern Station, more frequently than usual) from defects in the connexions of the Railway Telegraph. Time-signals are sent daily to great distances, as Glasgow and Cardiff, and on the principal railways in various directions. Time-signal-guns are fired daily at Newcastle and Shields. The Post-Office Clocks are regulated mechanically, and signals are sent for regulating the Westminster Clock; and all these, as well as the Deal Ball, automatically report to us the success of the effect of the current which left the Greenwich clock. I shall advert below to the failure of my proposal for hourly time-signals on the Start Point.
In these various operations, about one-fourth of the strength of the Observatory is employed. Viewing the close dependence of Nautical Astronomy upon accurate knowledge of time, there is perhaps no department of the Observatory which answers more completely to the original utilitarian intentions of the founder of the Royal Observatory.
I expect that, in the latter part of the summer, steps will be taken by Mr. Otto Struve for the telegraphic determination of the differences of longitude, between Greenwich and some station on the Continent, and between Greenwich and some point near Milford, as portions of the great Arc of Parallel which is to extend from Orsk on the river Oural to Valencia, The initiation of this enterprise was made by Mr. Struve, and much of the primary work was done by Mr. O. Struve. I hold it to be my duty therefore in no way to interfere with Mr. O. Struve's plans; but to place the Observatory, and myself, and the influence which I may command among the telegraphic or other institutions of the country, entirely at his service; and, as a zealous subordinate, to take every possible measure for carrying out his design.
XIV, Personal Establishment. –
The persons employed as Assistants are the same, and with the same ranks, as at the last Report; … Mr. Dunkin is charged with the Altazimuth; Mr. Ellis and Mr. Criswick with the Chronometers and Time-work; …
XVI. General Remarks. –
Before closing this Report, I take the opportunity of placing on record some plans of proposed action, which I am unable to carry out at present; but which, as I trust, with such modifications as experience may suggest, will be adopted for effectual use at some future time. They relate to the system of hourly time-signals proposed for exhibition at the Start Point.
It will be remembered by the Board of Visitors that, after consideration of the reasons which I adduced and the methods of galvanic communication and manipulation which I explained, the Board, at their Visitation of 1862, deputed a selection of their Members, accompanied by myself, to wait on His Grace the First Lord of the Admiralty, and to request his favorable attention to the proposal; and that in the course of the summer of 1862, an answer was received, conveying the substance of communications referring to this proposal which had passed between the Board of Admiralty and the Board of Trade, of which the conclusion was, that the Board of Trade possessed no funds applicable to the defraying of the expenses attending the execution of the scheme. This answer was not laid before the Board of Visitors or known to myself till the Visitation of 1863. As it did not fully explain the intentions of the Board of Admiralty, I applied to them in the autumn of 1863, requesting to be informed whether the Admiralty considered as possible the establishment of these time-signals under their own authority; and I received their reply that they do not at present contemplate that measure.
Trusting that the establishment of these signals is only deferred for a few years, and thinking it probable that advantage may result to the system, which will hereafter be adopted, from a publication of some details of the plan on which I had proposed to act now, I will here state the general principles of the arrangement on which I had pro- visionally decided.
The Admiralty possess telegraphic wires passing underground from the Admiralty Telegraph-Office in Whitehall through the principal street of Deptford, towards Deptford Dockyard, Woolwich, and more distant places. The Royal Observatory possess telegraphic wires passing from the Observatory to a house in Deptford called Gothic House, through which one of the Admiralty wires is led; and here, at any moment, such communications of wires can be made, that the galvanic currents from the Admiralty will all pass to the Observatory and back to Gothic House (by what is technically called "a loop"), and thence proceed towards Deptford Dockyard and Woolwich.
When an interruption is made at the Observatory, then currents can be sent direct from the Observatory to the Admiralty-Telegraph-Office.
The wire of the Deptford-speaking-instrument in the Admiralty-Telegraph-Office can be joined with a wire of the Devonport-speaking-instrument in the same office. The wire from the Telegraph-Office to Devonport is continuous, and is good, liable only to some interruptions from occasionally receiving the spray of the sea beyond Exeter.
When these connexions are made, there is unbroken metallic communication from the Royal Observatory to the Admiralty-Office at Devonport; sufficiently good to insure the transmission of Greenwich signals with the regularity required for giving the information by which the Devonport Superintendent can adjust his clock; and also sufficiently good to insure the transmission of automatic signals from the Devonport clock to Greenwich, by which the officers of the Royal Observatory will see the error of the Devonport clock; but not sufficiently good to insure the regular dropping of a time-signal at the Start, if wires should be continued from any part of the Devonport telegraph-wire to the Start.
The distance, however, from Devonport to the Start, is so much less, that it may be expected that no difficulty will be experienced in dropping a time-signal at the Start by the agency of a galvanic battery and automatic clock at Devonport.
The first section then of the proposed operations must consist in such arrangements as will secure the accuracy of a clock at Devonport, and the second section must consist in such arrangements as will secure the accuracy, (by automatic action of that clock), of the signal-drop at the Start, and will also secure a register at Devonport (by automatic action of the Start mechanism) of the actual success of the signal drop, in a form which will admit of convenient transmission to the Royal Observatory of Greenwich.
For the first section, three arrangements are to be made. (1.) About the time of each of the proposed communications from Greenwich to Devonport or from Devonport to Greenwich (in all, three times or four times every day), for a few minutes at each time, an automatic clock at Greenwich must interrupt the Greenwich loop, and must connect the Greenwich Motor Clock with the Deptford wire to the Admiralty; and an automatic clock at the Admiralty must interrupt the communications of that Deptford wire with its speaking-instrument, and of one Devonport wire with its speaking-instrument, and must connect the Deptford wire with the Devonport wire. (2). At the times arranged for signals from Greenwich to Devonport, the Motor Clock at Greenwich must for an instant automatically take its wire from earth and connect it with a galvanic battery. (3). At the times arranged for signals from Devonport to Greenwich, the Devonport Clock must for an instant automatically take its wire from earth and connect it with a battery. All these arrangements are very easy, and their action is practically infallible.
The Devonport Clock would probably require a small mechanical correction every day (to remove the error, arising from unsteadiness of rate; which error the attendant would ascertain by observation of the Greenwich signals.) This is best done, as at Greenwich, by fixing on the pendulum a magnet, of which one pole swings above a galvanic coil; a galvanic current, sent at pleasure through the coil, produces attraction or repulsion, according to the nature of the current sent; and the clock is accelerated or retarded. The current must be kept in action till the clock-error is perfectly corrected.
In this manner, it was presumed, accuracy would be insured in the state of the Devonport clock sensibly equal to that of' the Greenwich Motor Clock; and thus Devonport might be adopted as basis for, the operations by which the Start time-signal would be actually dropped.
For the second section, the arrangements would be the same as those between Greenwich and Deal. There must be a clock at the Start, by which the resident at the Start would be guided in order to raise the Start signal at the proper time before each hour; there must be a relay and a local battery; the Devonport clock, by mechanism similar to that of the Greenwich Motor Clock, must automatically send a current accurately at every hour, which will work the relay and put the local battery in connexion; and the action of the local battery must withdraw the detent on which the time-signal is lodged, and thus drop the signal ; and the signal, shortly before reaching its lowest point, must (by what is called a " tapper-apparatus") so change the connexions of the battery that an instantaneous current will be sent to Devonport. These arrangements are found, in practice, to work without failure.
It was proposed that the time-signal at the Start should be a skeleton-ball about 8 feet in diameter, dropped through a space of 12 or 16 feet. The locality selected for it is a rock behind the Start lighthouse, called" The Boy." The height of the mast on which it should be raised would be determined after inspection from the sea; but no great height would in any case be necessary. It was proposed to commence with day-signals only; but night. signals would be given by a mere change of galvanic communications at the Start, which would enable the galvanic current to drop a small weight, whose fall would fire a quantity of gunpowder sufficient. to produce a flash visible at the distance of several miles.
For the Devonport record of the currents sent by the action of the tapper-apparatus at the Start, the following mechanism was proposed. The Devonport clock was to give rotation to a small barrel, perhaps 3 inches long and 3 inches in diameter, covered with paper. This barrel was to revolve in a time differing from 1h by a small quantity, say by 1/900 part, which would easily be given by the 60-minute spindle of the clock, carrying a wheel of 30 teeth acting in one of 29 teeth, the latter wheel being fixed to one of 30 teeth acting in the barrel-wheel of 31 teeth. The Devonport clock also was to give slow motion by a screw to the frame carrying an indicator which would be made to travel nearly from one end or the barrel to the other in 24 hours. That indicator would he made to impress a point (m the barrel by the instantaneous current from the tapper-apparatus. It will be seen that the 24 signals given in the course of one day, if at perfectly uniform intervals, describe on the barrel a spiral very little inclined to the axis. Any departure from uniformity to the extent of 3 seconds of time would immediately be visible to the eye; and this would be sufficient to give evidence on the correctness of management of the ball. At the end of 24 hours exactly, the barrel would have performed 24 + 24/900 revolutions. In preparation for the commencement of a second day. the attendant must draw hack the travelling indicator-frame to the beginning of the screw, and then the indicator would in the course of the second day describe another spiral at the distance 24/900 x circumference of barrel from the former. This retraction of the indicator-frame is the only daily operation, referring to the register, which is required from the attendant. At the end of each month, the barrel must be removed and replaced by another; the paper covering is then to be taken off and sent to the Astronomer Royal. For the indicator I proposed to use a mechanism (suggested to me by Professor Wheatstone) in which the bottom of a small cistern of ink is perforated with a single hole too small to permit the escape of the fluid ink; the action of the galvanic current thrusts a small wire through this hole, and the end of the wire carries a small film of ink which impresses a dot upon the barrel-paper.
In selecting a course for the telegraph-wires from Devonport to the Start, it was proposed, under the advice of the best Telegraph-Engineers, not to take the shortest line (which would be, to return towards London as far as the Kingsbridge Road Station, and then to pass by an inland road directly towards Kingsbridge, and the Start Point), but to make use of existing poles to Newtown Junction, Torquay, and Dartmouth, from which place the extent of telegraph line upon new poles would be small.
The following collateral advantages would attend the establishment of this system of signals. Accurate time-currents would be given at Devonport, which could be made subservient to the public exhibition of time-signals, either at Mount Wise, or on the Devonport Column. A commencement would be made of coast-telegraph, available for military purposes. Facilities would be given for a commercial telegraph from the Start Point to Dartmouth, much desired by persons connected with the mercantile marine.
IT is convenient on the present occasion to limit my Report to the period commencing 1864, May 20, and terminating 1865, May 10. The arrangement which I have maintained for many years is adopted without alteration.
1. Buildings and Grounds. –
The two piers which are built in the Front Court, as well as a third pier built in the Magnetic Ground, having been used nearly in the way proposed for the observations connected with the Great Arc of Parallel (as will be hereafter mentioned), the portions of the piers which projected above the ground have been taken down; their capping-stones being left at the surface of the ground, with an inscription engraved on each for its identification.
Our telegraphic communications of every kind were again destroyed by a snow-storm and gale of wind which occurred on January 28, and which broke down nearly all the posts between the Royal Observatory and the Greenwich Railway Station. They were restored after a time, without alteration of plan, (except in the instance of the wire appropriated to the Electric and International Company, which, by request of that Company, and at their expense and under their superintendence, was placed underground,) but with general renovation.
The only change of Buildings which I contemplate as at present required is the erection of a fire-proof Chronometer Room. The pecuniary value of Chronometers stored in the Observatory is sometimes perhaps as much as 8,000[pounds]l. I do not see that this can be done in any other way than by retaining the present room (the room above the principal Computing Room), making fire-proof floor and ceiling, and stripping the old pannelling from the walls.
Among the buildings of the Royal Observatory, I may now class the Time-Ball-Tower at Deal. On occasion of the sale of the Navy Yard at Deal, the Time-Ball-Tower, at my representation to the Admiralty, was specially reserved j and, as there is now no competent resident authority for its superintendence, it is placed generally under the care of the Astronomer Royal. Beyond this announcement I have no special remark to make.
V. Astronomical Instruments: –
The Transit-Clock is in good order. Occasionally it has been stopped a few seconds through the retention of its wheel-teeth by the galvanic springs.
The Barrel-Clock of the Chronograph required, in the last winter, some repairs in the pivot-bearings, the round holes having been worn into an elongated and irregular form. Preparations have been made for altering the mechanism of water-resistance to the pendulum, so as to make it resemble that of the clock-movement of the South East Equatoreal; and the new apparatus has not been fixed, merely because the uninterrupted use of the barrel was required in connection with observations for the longitude of Glasgow Observatory.
The Motor Clock is in good order; and, since the abstraction of pendulum-contact-springs mentioned in the last Report, preserves a steadier rate than formerly. The Visitors are aware that, for producing those very minute changes of rate for a small time which are required to correct the petty errors of indication that arise in the course of a day, there is fixed to the pendulum a small steel magnet, which swings over a galvanic coil, through which currents of either character can be sent, the coil then having the property of attracting or repelling the magnet, and thus accelerating or retarding the vibrations of the pendulum. We now avail ourselves of the presence of the same magnet to effect the larger adjustments of clock-rate without stopping the clock. A vertical piece of iron wire is fixed by friction in a piece of wood projecting from the back of the clock-case, so that. the upper end of the magnet swings under the end of the wire; and by raising or lowering the wire, the clock-rate is less or more accelerated.
The apparatus for home-use and for distribution of galvanic currents at definite times is in good order.
XIII.-Chronometers, Communications of Time, Longitudes, &c.
A short time- since the number of Chronometers on hand exceeded 200. On May 10, the number is 175, thus distinguished :-Chronometers the property of Government, 110; Chronometers the property of chronometer-makers, on the annual competitive trial, 47; Chronometers on trial for purchase by the Government, the property of makers (to be taken in exchange for dilapidated Chronometers, or to be tried as deck-watches), or the property of Officers of the Royal Navy, 11; Chronometers on trial for the India Store Department, 7. There are also 2 clocks on trial, for the India Store Department, All Chronometers on trial are rated every day, by comparision with one of the clocks sympathetic with the Motor Clock; a portion of the Government Chronometers, far more than sufficient for probable wants of the service, are also so compared; the remainder are compared every week. Every Chronometer, whether on trial, or returned from a chronometer-maker as repaired, is tried at least once in the heat of the Chronometer-Oven, the temperature being usually limited to 90o Fahrenheit; and, guided by the results of very long experience, we have established it as a rule, that every trial in heat be continued through three weeks.
The decision on the merits of Chronometers, tried for purchase or for classification in merit, rests with me: it is a troublesome and responsible work, but the principal part occurs only once a year. The repairs of Government Chronometers are managed entirely under the superintendence of the observatory, and are a source of continual correspondence and trouble of various kinds.
The system of sympathetic clocks of Mr. Shepherd's construction includes seven, of which the most worthy of attention are, the Motor Clock, the large Public Clock, the Clock for Chronometer-comparisons, and a small clock no bigger than a chronometer fixed in the computing-room. The same galvanic current gives motion to the train of wheels in each of these clocks; and as the contacts completing the galvanic circuit are made by one pendulum (below the Motor Clock), it is only necessary, for their regulation, to regulate that pendulum. This is effected in the computing-room, by means of a commutator affecting the current of a subsidiary battery, by which a current of either kind is sent through a coil, which is fixed to the case of the Motor Clock in such a position that a steel magnet carried by the pendulum swings just over it.
There is another small sized clock in the computing room of a different construction, sympathetic with the Transit-Clock; and the comparison of the Transit-Clock with the Motor Mean Time Clock, for determination of the errors of the Motor Clock, is in fact effected by the comparison of their sympathetic representatives in the computing-room, where also is the commutator by which the corrective action above mentioned is applied to the pendulum of the Motor Clock, accelerating or retarding it as long as may be necessary to correct its error of indication.
The same current from the Transit-Clock regulates a clock in the S.E. Equatoreal room (on Mr. R. L. Jones' principle), and drives a chronometer on the eye end of the S. E. Equatoreal telescope.
The whole of this system is in good order, excepting the telescope-chronometer, which is not perfectly efficient. I am trying a new construction of regulating (not driving) a chronometer by galvanic current.
A galvanic circuit passes through the face of the Motor Clock by a wire which is interrupted at two places, where junction is made at every 60 minutes and at every 60 seconds respectively. Thus an accurate current is sent every hour, discharging the detent of the Time-Signal-Ball (which however is used only at 1h P.M.) and working a relay which sends hourly currents to the South Eastern Railway Station, London Bridge, the Electric and International Telegraph Company's Office, and the Office of the London District Telegraph. At the S. E. R. Station is a clock, the property of the Royal Observatory, and governed by a current at every second from the Royal Observatory; by the mechanism of this clock, the course of the hourly current is determined. At 1h. P.M. it is sent to Deal to drop the Time-Signal-Ball there; the establishment connected with that Time-Signal-Ball is now entirely subordinate to the Royal Observatory, and for that public Signal, but for no other, the Astronomer Royal is responsible. At other hours the current goes to different stations on the S. E. Railway, at the discretion of their Telegraph Superintendent, Charles V. Walker, Esq. F.R.S. The seconds current is made useful to private Offices in London. At the Office of the Electric and International Telegraph Company, the Superintendent, Cromwell F. Varley, Esq., has mounted very beautiful apparatus for distributing the signal over various lines of railway reaching almost to the extremities of Britain, and for firing signal guns at Newcastle and Shields. The currents sent at every hour to the Office of the London District Telegraph are made available to chronometer-makers.
Signals of a less public character are sent to the Clocks of the Post Office and to the Clock on the Westminster Palace, and for these the Astronomer Royal is responsible.
In the instances of the Deal Signal Ball, the Post Office Clocks, and the Westminster Clock, the instruments automatically report their own state, which thus becomes immediately known to us.
I am informed that the value of these public signals is rising very much in general estimation.
The whole system is in a perfectly efficient state.
This extensive arrangement is founded entirely on amicable agreements made by me with the different commercial companies, on the basis of mutual assistance; nominal payments being made, as royalties, for the use of the poles on which the wires are stretched, and for small repairs. The establishment of the wires for earth-currents is on a similar footing.
I can hardly doubt that there will soon be movements in London, as in other great cities of our Empire, for more perfect regulation of Public Clocks, and for other exhibitions of Time Signals. The business of the Royal Observatory, in reference to such proposals, will consist mainly in the transmission of currents accurately at every hour, or every minute, or every second, to definite offices in London; and to this I shall be prepared to give all the attention which it can require.
In conformity with arrangements made by Professor Argelander and Mr. Otto Struve for measures of differences of longitude on various parts of the Great European Arc of Parallel, observations were made in the summer and autumn of last year for determining our differences of longitude with Bonn, with Nieuport, and with Haverford-West. In carrying out these operations, I had the pleasure of seeing Colonel Forsch and Captain Zylinski (of the Russian service), and Dr. Thiele (attached to the Observatory of Bonn). Every assistance was given by the Telegraph Companies whose systems of telegraph connected the various points with London. The plan of operations which was adopted, though beautiful in theory, was better adapted to a steady climate, uniform over a large district, than to a climate so unsteady as that of the British Islands; and in consequence the determinations became very laborious. Every part, I believe, was finally carried out to the perfect satisfaction of the observers, with only this insignificant anomaly, that their final longitude was referred to a point in the Magnetic Ground, marked as "Forsch's Transit," and their final latitude to a point in the Front Court, marked, as "Zylinski's Vertical Circle." I am not yet in possession of the numerical results.
Operations have been going on, and will probably have been finished at the time of the Visitation, for determining the longitude of the Observatory of Glasgow. Professor Grant has adopted the method of observation of the same catalogue of stars at both. stations, and of chronographic registration of all the transits (whatever might be the place of observation), at both stations.
XIV. – Personal Establishment.
Other Assistants in the order of seniority are: Mr. Dunkin, who is charged with the …; Mr. Ellis, who, acting as astronomical observer, has the special care of Chronometers, Galvanism, and Time-work generally, and also of Money Accounts; Mr. Criswick, who, also observing generally, sometimes assists Mr. Ellis, and sometimes takes part in astronomical reductions; …
XV. Extraneous Work.
It will readily be understood by the Visitors that the longitude-operations, to which I have alluded, have interfered much with the regular business of the Observatory, but, beyond that reference, I have no further remark to make.
The Report which I last presented to the Board of Visitors was brought up to 1865 May 10. The present Report terminates on 1866 May 14, applying to the state of current business on that day, and to the principal occurrences between the two days specified. The Heads of Report are the same as those which I have adopted for many years.
I. Buildings and Grounds:–
On 1865 May 23, a thunder-storm of great violence passed very close to the Observatory. After one flash of lightning, I was convinced that the principal building was struck; and while on my way to seek for marks of injury, I saw another flash strike Greenwich Hospital. No very certain marks of the first flash were seen upon the lofty building of the Observatory; but. several galvanometers in the Magnetic Basement were destroyed. Lately it has been remarked that one of the old chimneys of the principal building had been dislocated and slightly twisted, at a place where it was surrounded by an iron stay-band led from the Telegraph Pole which was planted upon the leads of the Octagon Room; which stay-band (intended only as a guard against accidents) had never sustained and could never have exerted any mechanical force. The top of the Telegraph Pole was furnished with seventeen sharp spikes; and was connected with the iron stay to the chimney, an iron conducting-rod to the leads, two iron wires more than 400 feet long to the Magnetic Basement, and nine iron wires more than 800 feet long across the Park. It appears therefore that the electric current was divided into at least two courses, namely by the iron stay to the chimney and by the iron wires to the Magnetic Basement. It also seems probable that the cluster of sharp spikes had attracted the electricity in one shock, instead of drawing it off gradually. The Telegraph Pole has lately been removed.
The snow-storm and gale of wind on 1866 January 11, which caused so much interruption in all the telegraphs of the south of England, completely destroyed the open-air telegraphic communications of the Royal Observatory; and our partial telegraphic service has since then been carried on through some spare wires accompanying that of the Electric and International Company to which I alluded in my last Report. On consideration of the serious interruptions to which we have several times been exposed from the destruction of our open-air Park-wires and street-wires, I have made an arrangement for leading the whole of our wires in underground pipes as far as the Greenwich Railway Station. Repeated delays have occurred, such as are almost unavoidable where the interests of several companies are concerned; and finally, it has been found impracticable to reinstate all our communications until a new subaqueous cable shall be laid across Deptford Creek. At present therefore the galvanic lines for the earth-currents, and those for occasional communication with an Admiralty line, are interrupted. On completing these lines it is proposed to dismount the turn-plate which is intended for Admiralty communication, from the Gothic House at Deptford, and to fix it at the Deptford Station where the South Eastern Line crosses the Admiralty Line.
The Tower at Deal for the Time-Signal-Ball has been properly inclosed and fitted for the residence of the Ball-Attendant.
I alluded in my last Report to the demand for a fire-proof Chronometer Room; and to the scheme of rendering the present room fire-proof. With the sanction of the Board of Admiralty, I have had some consultations with the Admiralty Surveyor of Buildings on this proposal. So many difficulties, however, appear, that for the present I withdraw that plan. But it is desirable to keep the matter in view, both for the purpose of insuring the safety of the Chronometers, and for the Purpose of gaining room. I believe that it will be practicable, by withdrawing a number of Chronometers from rating or winding, to store them in such a manner that the present pressure for room may be relieved, but it is desirable that we should not feel ourselves driven to that resource.
V. Astronomical Instruments.
Some irregularities in the rate of the "Transit Clock appeared to be due to the weight and power of the springs, especially to one of the two pairs, which are used to produce galvanic circuits at every second of transit-clock time. These have been made lighter, and there appears to be no doubt that the rate of the clock is improved.
In the Chronograph-Barrel-Clock, the proposed alteration in the mechanism of the water resistance has been made, and with advantage. The Visitors are aware that in this clock, and in that of the South East Equatorial, it has been my object to give the necessary tangential resistance to the conical pendulum in a form that produces no centripetal pressure; which is effected by means of a bell-crank lever in which the recess of the pendulum from the center dips a small spade into water. In order to avoid change of relative elevations, I had used an ill-arranged apparatus for the Chronograph pendulum; I have now made the small difference of elevations, and have introduced an apparatus similar to that of the South East Equatorial.
There seems to be friction, not yet thoroughly traced out, in the upper wheels of the clock. And we suspect an error in the compensation of the pendulum; but it is not easy to make experiments upon it.
The Motor Clock, employed for action of every kind which requires the use of accurate Greenwich Mean Solar Time without the need for numerical correction, is in good order; preserving a sufficiently steady rate, with great uniformity of arc of vibration. I have formerly mentioned that a steel bar-magnet, parallel to the pendulum rod, is carried by the pendulum-rod; mounted originally in order to give us the power, in the computing-room, of accelerating or retarding the vibrations during a limited time, by throwing a galvanic current of one or other kind into a fixed coil which is placed below the magnet, and lately used for general adjustment of the clock-rate by bringing a piece of iron, fixed in the clock case, nearer to or further from the other pole of the steel magnet. The last mentioned apparatus is so convenient that I can recommend its use for clocks in general.
The galvanic apparatus for distribution of currents consists of the following parts. First, a contact is made at every swing of the pendulum, which sends the current that drives the wheel-work of all the sympathetic clocks, and also works a relay by which we distribute any number of seconds'-currents. Secondly, in the course of a wire which passes through the clock-face, there are two interruptions, of which one is closed a short time before and after every 60m , and the other is closed at 60S exactly; the circuit thus formed precisely at every hour works a relay by which accurate hourly currents are distributed. Thirdly, the connexions are altered at certain portions of the hour, so as to enable us to receive return-signals from the Deal Ball, the Westminster Palace Clock, and the Post Office Clocks.
In my original construction of the Equatoreal, two pairs of galvanic wires were led (by means of insulated rings and touching-springs, at the polar and declination pivots) to the eye-end of the telescope; one pair being for galvanic contact, to make impressions on the Chronograph register, the other pair being intended to drive a galvanic chronometer in sympathy with the Transit-Clock. The chronometer, though sometimes acting well (as in the Eclipse Observations of 1860), often gave us a great deal of trouble. At last I determined, on the proposal of Mr. Ellis, to attempt an extension of Mr. R. L. Jones' regulating principle. It is well known that Mr. Jones has with great success introduced the system of applying galvanic currents originating in the vibrations of a normal pendulum, not to drive the wheel-work of other clocks, but to regulate to exact agreement the rates of their pendulums which were, independently, nearly in agreement; each clock being driven by weight-power as before. The same principle is now applied to the chronometer. I supplied an old worthless half-second chronometer; upon the axis of its balance a small magnet is fixed (its centre being pierced by the balance-staff), a coil in the fixed part of the chronometer embraces this magnet as in the ordinary galvanometer, and a current is sent through the coil at every second of the Transit-Clock. The construction is perfectly successful; the chronometer remains in coincidence with the Transit-Clock through any length of time, with a small constant error as is required by mechanical theory. The only inconvenience is, that the beats can scarcely be heard; I propose to introduce a small galvanic magnet, merely to make an audible sound.
The intromission of the water which drives the clock-movement has been managed with great convenience to the observer, by a screw apparatus in the Equatoreal Room which regulates the tap in the basement. For the purposes of experiment, I am also introducing a means of throwing on the water by another tap in the lower story.
XIII. – Chronometers, Communications of Time, &c.
The number of Chronometers now on hand is 217; consisting of the following different classes. Admiralty Box-Chronometers 124; Pocket Chronometers 16; Deck Watches 11; Deck Watches on trial 9; Makers' Chronometers 011 Annual Competitive Trial 56; on trial for a Department of Government 1. The Competitive Chronometers, the Government Chronometers lately received after repairs, and still under trial for steadiness and compensation, and the Chronometers under orders for issue, are rated every day; all others, once a week. Every Chronometer is at some time tried in heat, to a temperature of goo Fahrenheit, for three weeks.
The judgment of the comparative merits of Chronometers is made by me, and the management of the repairs of Chronometers is effected by me, or under my immediate superintendence.
The system of sympathetic clocks is used without alteration, and with great convenience and advantage. It is an important part of this principle that a person sitting at a desk in the computing-room can compare distant clocks (sidereal with solar), can mechanically correct the error of the solar clock, and will by this act necessarily correct the clock used for chronometer-rating, and the clock used for exhibiting and distributing time-signals.
By the principal corrected solar-clock or "Motor Clock," currents are sent at every second to regulate an Observatory Clock of peculiar construction at London Bridge, by which the distribution of communications is changed. Then by the Motor Clock, hourly signals are sent on the S.E. Railway, one of which drops the Deal Time Ball (under my official superintendence); and hourly signals are sent to the Office of the Electric and International Telegraph, whence, by means of mechanism arranged by Mr. Varley, and now under the care of Mr. Culley, they are distributed over Britain and fire guns at Newcastle and Shields. The apparatus at the Post Office in connexion with the Royal Observatory is at present receiving some changes, but will shortly, I expect, be in an efficient state. Signals are sent to the Westminster Clock for the guidance of its manager, and that clock, as well as the Post Office Clocks when in proper connexion, automatically send signals to inform me of their state; these return-signals are sent at minutes intermediate to the integral hours, when the Motor Clock has made new arrangements for exhibiting return-signals instead of sending signals The signals through the London District Telegraph for Chronometer-makers are not yet restored. Some signals go to the offices of private merchants in London.
The British Horological Institute have brought before the Court of Common Council of the City of London, the subject of Public Time Signals of accurate character in London; but I do not know the present state of the transaction.
I retain the intention of repeating the proposal, when circumstances shall appear favourable, for exhibiting an hourly time-signal on the Start Point; and, in the restoration of our wires, some arrangements are made with that subject specially in view.
XIV.-Personal Establishment.
The Assistants whose names are borne on the Government Books are; Mr. E. J. Stone, M.A., Fellow of Queen's College, Cambridge; Mr. J. Glaisher, F.R.S.; Mr. Dunkin; Mr. Ellis; Mr. Criswick; Mr. Lynn, B.A., Univ. London; Mr. Carpenter; Mr. Nash. To these gentlemen respectively are assigned the duties of: – Confidential Assistant; – Superintendent of the Magnetical and Meteorological Department; – Superintendent of Altazimuth and of standing adjustments of Transit Circle; – care of Chronometers, Galvanism, Time Work, Money Accounts; – general observation and reductions; – control of Supernumerary Computers in the Astronomical Department; – general and equatoreal observation, with care of Library, Manuscripts, and printed works issued by the Observatory; – and assistance in the Magnetical and Meteorological Department.
XVI. – General Remarks.
Every successive year adds something to the annual labours of the Observatory. This arises, not simply from the occasional additions to its general plan of work (as in the extension of Lunar observations by the Altazimuth, the distribution of time-signals, &c.), or from the rise of new astronomical wants …
IN order to allow myself sufficient leisure for careful reference, in preparing this Report, I have made it to terminate on 1867, May 3. The interval between the times to which the last Report and the present Report apply is twelve lunations. The general plan of the Report is the same as that which has become customary in my Reports to the Visitors.
I. Buildings and Grounds:–
When geodetic operations were commenced in 1787, for connecting the observatories of Greenwich and Paris, a double truss was constructed, spanning over the roof of the Octagon Room and bearing upon its walls; and 011 this truss Ramsden's theodolite was supported above the center of the roof. The observing-hut or cabin which covered it was planted on the flat roof itself. The truss, being rotten, was removed by me about 1837, hut the cabin remained, and had by degrees been loaded with various instruments. As I began to fear for the safety of the flat roof, I have had a single truss constructed near the south side of the roof, spanning from the south-east wall to the south-west wall; and one side of the cabin is carried by this truss, the other side bearing directly on the south wall. In this way, the pressure on the flat roof is entirely avoided.
The room above the Principal Computing Room is at present devoted to the custody and rating of Marine Chronometers, the property of the Government, or on competitive trial. In the event of making the changes in the building of the South-East Dome to which I shall immediately allnde, the chronometers will be removed from this room, and it will be occupied by Computers.
In the South-East Dome and the two stories of building below it, no alteration has been made; but the following alterations have been sanctioned by the Board of Admiralty and by the House of Commons. By proper alterations of the three floors, the staircase, and other portions of the building, every part below the wooden dome is to be made fire-proof. Then it is intended that the Chronometers shall be transferred to the middle room; and the Supernumerary Computers, who now occupy that room, will in future work in the room above the Principal Computing Room. In this manner, besides attaining the object which I have long had at heart, the giving security to the Chronometers, I shall at the same time give security to the South-East Equatoreal, and shall place the Supernumerary Computers in more convenient proximity to myself and the Assistants.
Our eight telegraph wires are now led (by arrangement with the Electric and International Telegraph Company) underground to the Greenwich Railway Station, and thence on the poles of the South-Eastern Railway, and by a cable under Deptford Creek. At Deptford Station, by the liberal permission of the South-Eastern Company, a turn-plate is fixed, into which two of our wires are led; and from the Admiralty wire which passes through the High Street of Deptford, a loop is led into the same turn-plate, so that the Admiralty loop can practically be extended into the Royal Observatory, and can, when necessary, be interrupted there. I have been desirous of maintaining this command of wire, with the hope that I may yet have occasion to use it for the transmission of signals to Devonport in reference to the exhibition of' time-signals on the Start Point, or in other directions for similar purposes.
V. Astronomical Instruments:–
The rate of the Transit-Clock is not yet quite satisfactory. I thought it possible that the galvanic action in the pairs of springs used for galvanic communication might, in some unexplained way, affect their resistance to the teeth of the clock wheel; but I have not yet discovered any difference of rate or of vibration-amplitude dependent on the completeness of the galvanic circuit. The compensation has not been strictly examined.
One of our old clocks with gridiron-pendulum has gone so unsteadily that I suspect a sticking-fast of the metal rods in their cross frames. The pendulum is now undergoing a thorough cleaning.
Attention has been given to the compensation of the Chronograph Barrel-Clock pendulum, and its rate is now very steady.
It is known to the Visitors that the one-second-punctures on the Barrel-Sheet follow each other on a spiral whose interval of coils is one-tenth of an inch; and that, for easily reading these, an impressed spiral line is necessary. Hitherto, the spiral line has been traced by ink flowing from a glass pipette. The difficulty, however, of procuring pipettes suitable to our wants has induced us to employ the continuous indenture produced by a steel point. It requires the application of greater force for turning the barrel under it, but in other respects it is very satisfactory.
The Motor-Clock is in good order. This clock is kept to Mean Solar Time with all the accuracy that we can give to it, by application at pleasure of magnetic or galvanic attraction or repulsion on a magnet fixed to its pendulum. It is used to maintain several clocks in the Observatory to accurate Mean Solar Time, and to distribute seconds' galvanic currents and hourly galvanic currents (the latter through England); and also to change connexions of wires which enable us to receive signals from distant clocks and time-balls.
One of our sympathetic clocks has given some trouble; I believe from a combination of faults of wire and faults in the clock, now corrected.
The South-East Equatoreal is in excellent order. … The chronometer carried at the eye-end of the telescope, and adjusted by galvanic regulating action to exact sympathy with the Transit Clock, is perfectly successful. To give audible indications of the seconds' currents, one of the old galvanic chronometers is used.
The water-clock which gives motion to the Equatoreal, it is known, is driven by the force of water from the ordinary supply pipes acting through a turbine, the opening of the last tap being determined by Siemens' Chronometric Governor. The mean velocity of the clock, as I believe, does not depend upon the openings of the preceding taps, but the rapid inequalities of velocity do depend on them in a way which it is very difficult to explain from theory. A tap has now been established in the immediate vicinity of the water-clock, and by experiments on this we have acquired complete mastery of the instrument. It can now be made to move uniformly, without any sensible inequality, and with astronomical accuracy.
The train of wheel-work was rather noisy. For one of the wheels, made of iron, a wooden wheel has now been substituted by Messrs. Ransome, and the spindle is carried through a box stuffed with wool (not in contact with the spindle); and the noise is much deadened.
XII I.–Chronometers, Communications of Time, Determinations of Longitude:–
On 1867 May 3 we have on hand 192 chronometers; thus classified: 95 box-chronometers, 14 pocket-chronometers, and 10 deck-watches, the property of the Admiralty; 17 on trial for purchase, to replace six bought by the Japanese authorities; 55 makers' chronometers on competitive trial. All chronometers, except those which have been in our hands so long that we have great familiarity with their rates, are compared every day with a clock which is sympathetic with the Motor Clock; those in the excepted case are compared once a week. All are subjected to some weeks trial in a temperature not exceeding 90° Fahrenheit.
All estimations of the value of chronometers to be purchased, and all superintendence of repairs, rest with me.
For issuing chronometers to the outports, a new system of packing has been introduced. It is found that with reasonable attention, the chronometers can be sent safely by railway to almost any distance.
The following table, showing the gradual improvement in the steadiness of chronometers from 1851 to 1866 may be interesting to the Visitors. Through this period the system of trial has been almost perfectly uniform. The" trial number" is a combination of changes of weekly rate, in the form which I consider as on the whole fairly representing the fault of the chronometer; it always exceeds in some measure three times the largest change of weekly rate from week to week. The number here given is the mean of the trial-number for the six best chronometers of each year.
1851 - - 38.0s 1859 - - 32.0s
1852 - - 41.3s 1860 - - 27.9s
1853 - - 52.5s 1861 - - 29.9s
1854 - - 34.8s 1862 - - 25.8s
1855 - - 40.6s 1863 - - 21.8s
1856 - - 52.6s 1864 - - 22.6s
1857 - - 46.1s 1865 - - 22.7s
1858 - -29.1s 1866 - - 21.2s
The Motor Clock, and the apparatus connected with it, are in good order. The Visitors are aware this clock is compared and regulated by an easy practical process, that it maintains various clocks in sympathy with itself, that it regulates clocks in London, sends signals through Britain, drops the Deal Time-Ball, fires guns at Newcastle and Shields (I think also at, Sunderland), and puts communications in such a state that we can receive automatic reports from the signal-places, as we may desire.
I may however specially mention that daily signals are now sent to some places in Ireland; and that, during the expedition of the Great Eastern for laying down the Atlantic Cable, time signals were sent on board twice a day, to enable her constantly to determine her longitude.
The following statement will show the general success of galvanic operations for dropping the time-signal at Deal. The distance by the wires is about 100 miles; there are several junctions of wires to be made, and on the whole it may be regarded as a very difficult line.
In the year 1866, communication was interrupted 13 days, from the destruction of wires by the great snow· storm. Through the rest of the time,
On 83.3 per cent. of the days, the ball was dropped in the orderly way, by the Greenwich current.
On 7.7 per cent. the current was weak (in nearly every instance from defective insulation in bad weather), and its action was assisted by hand.
On 4.8 per cent. no current passed (I think in every instance from interruptions on the long line of wire).
On 4.2 per cent, the wind was heavy and the ball was not raised.
The following statement will show the usual steadiness of the Great Clock on the Westminster Palace:-
On 38 per cent. of days of observation, the clock's error was below 1s.
On 38 per cent. the error was between 1s and 2s.
On 21 per cent. it was between 2s and 3s.
On 2 per cent. between 3s and 4s.
On 1 per cent. between 4s and 5s.
The Common Council of the City of London have declined to undertake the establishment of Public Time Signals.
Papers have been called for by the House of Commons regarding the proposal for establishing hourly time-signals on the Start Point, and have been printed and circulated; but no action has yet been taken on them.
The Ship-owners' Association of Liverpool have made inquiries on the facility of exhibiting an hourly time-signal on the Tuskar Rock. The expense would be considerable, but there would be no other difficulty. I believe that the Association have not yet come to a decision.
A most important determination of longitude has been made. In the autumn of 1866, various arrangements were made by me, with the view of determining the longitude of a primary point in Newfoundland, by galvanic currents through the Atlantic Cable, in the spring of 1867. However, in October of 1866, the authorities of the United States Coast Survey determined to act, and my friend Dr. B. A. Gould, having made an necessary arrangements at Heart's Content, and on arriving in London having secured the friendly assistance of the Directors of the Atlantic Cable, proceeded to establish a transit-instrument at Foilhommerun in Valencia. Advantage was taken of this opportunity for determining the longitude of Foilhommerun from Greenwich. After overcoming various difficulties, all operations were successful. I have been favoured by Colonel Sir Henry James, Superintendent of the Trigonometrical Survey, with the geodetic measure of difference of longitude between Foilhommerun and my first station Feagh Main; and I have the longitude of Feagh Main, found by different methods, as follows:
By chronometers in 1844 - - - - - - - - - - - - - - - - - - - - - - - - 41m23s.23
By galvanic communication with Knights Town in 1862 - - - 41m23s.37
By galvanic communication with Foilhommerum in 1866 - - 41m23s.19
Dr. Gould, immediately after his return to America, determined the arc of longitude from Heart's Content to Cambridge U.S. The collected results for longitude of Cambridge from different sources are,
By moon-culminators
Walker in 1851......................................4h44m28.42s
Newcomb in 1862-3...............................4h44m29.56s
By eclipses, Walker in 1851.........................4h44m29.64s
By occultations of Pleiades,
Peirce 1838-1842..................................4h44m29.91s
Peirce 1856-1861..................................4h44m30.90s
By chronometers
W. C. Bond in 1851...............................4h44m30.66s
G. P. Bond in 1855................................4h44m31.89s
By Atlantic Cable 1866................................4h44m30.99s
XIV.–Personal Establishment:–
The Assistants who are personally recognized by the superior offices of Government are: … Mr. Ellis, Manager of Chronometers, Galvanism, Time Work generally, and Money Accounts; … All these gentlemen make observations with any of the astronomical instruments.
XV.–Extraneous Work:–
We have had considerable labour in arranging for binding and issuing the impression of Sir T. Maclear's work on. the Verification and Extension of La Caille's Arc of Meridian.
I have the honor to offer to the Board of Visitors a Report, on the general transactions in the Royal Observatory, from 1867, May 3, (the date at which the last Report terminated,) to 1868, May 6, and on the state of the Observatory upon the last-mentioned day.
I. Buildings and Grounds:–
The room above the Computing Room is still occupied by the Admiralty Chronometers and Trial Chronometers. I hope in no long time to remove them to the South-East Dome, as I shall shortly mention.
In the South-East Dome, the alteration proposed last year for rendering the building fire-proof has been completely carried out, under the superintendence of the Admiralty Director of Works. For the wooden staircase, an iron staircase has been substituted. For the two upper wooden floors, there have been fixed floors carried by radiating girders and cross-joists of wrought-iron, whose flanges support light spars which are heavily plastered above and below, and finally carry floors of tiles; a construction which, as I understand is approved by the best builders of the present day. The lowest floor is paved with flagstones. For the middle room, which is to be appropriated to Chronometers (giving us much more space than we command at present), the requisite tables and shelves, with a Chronometer-oven larger than that which we use now, are in the workmen's hands, but are not yet mounted. In the lower room, I have separated a small space, by a partition of corrugated iron, to be used as Chronometer Office. When all these are ready, the Chronometers will be shifted to this room; and the room vacated by them (above the Computing Room) will be occupied by Computers.
In my last Report, Article VIII., I suggested, as a possible subject for future consideration, the providing of some extraneous room in which our accumulation of printed Productions of the Observatory might be deposited. … The materials removed from the old floors of the South-East Dome will supply to a considerable extent the wants of this building.
Our subterranean telegraph-wires were are broken by one blow, from an accident in the Metropolitan Drainage Works on Croom's Hill, but were speedily repaired. Two of the wires, which I have maintained and still maintain with the hope of application to the service of Time-Signals at Devonport and the Start Point, being at present unemployed, I propose to make use of them (with others) for a time, in a new modification of the Earth-Current-experiment, to be mentioned below.
II. Moveable Property:–
The portrait of John Dollnd is returned from the South Kensington Exhibition of Portraits: and the Clock, used at the Ashford Station for changing the communications of telegraph-wires, and thus giving connexion with the Time-Signal-Ball at Deal, is returned; the necessary adjustments being now made by hand.
V. Astronomical Instruments:–
The steadiness of the Transit-Clock has been improved by making the contact-springs lighter. We have reason to think that it requires a little more compensation for effects of temperature.
I have given a new form to the head of the clock, for admission of small tin boxes in which a few lumps of quicklime will, be placed, in order to keep the air about the wheel-work in a state of dryness.
The clocks generally are in good condition.
The Chronograph Barrel Clock continues to go well. The formation of the spiral line by pressure gives satisfaction.
The Motor-Clock, adjusted to Mean Solar Time, is in good order. This clock is an instrument possessing singular interest, from the nature of the process by which it is adjusted accurately to the Time which it is intended to exhibit; and from the mechanical structure by which, in conjunction with our galvanic apparatus and telegraphic connexion, it is employed in the rating of chronometers, in the distribution of time-signals through Britain, and in enabling us to receive automatic information of the state of various external clocks and time-signals.
All the sympathetic clocks are in good condition
The South-East Equatoleal is in the best order. … The stuffing-box for deadening the sound of the wheel-work has not yet been remounted; and perhaps some other small matters are not yet brought to their usual state. Everything essential, however, is in perfect order.
XII I.–Chronometers. Communications of Time, &c.:–
On 1868 May 6 we have on hand 162 chronometers. Of these, the following are the property of the Admiralty: 87 box-chronometers, 19 pocket chronometers, 9 deck-watches. The following are on trial for purchase: 1 officer's chronometer, 1 chronometer for trial of ship's speed. And of makers' chronometers on competitive trial there are 45. The system is maintained without alteration, of daily comparison of every chronometer (except those whose rates are well known to us) with an adjusted Clock of the sympathetic series, and of testing every chronometer in temperature of about 90 Fahrenheit for a few weeks.
The Board of Admiralty in all cases refer to me for estimations of the value of chronometers to be purchased and for superintendance of the repairs of Government Chronometers.
Among the various matters which cause anxiety in the chronometer-administration is one which, in a pecuniary view, is serious:– the msting of the balance-springs of chronometers while on service in the Navy. Experience inclines us to believe that the steel in its bright white state is less liable to rust than when it is blue. In order to make sure that no part of the mischief can arise from circumstances under our control in the chronometer-transmission, I have prepared a water-bath, in which all tow, &c. used in packing the chronometers will be dried for several hours.
The trial-number for the mean of the six best chronometers tried in 1867 is somewhat less than in any preceding year; shewing a continued improvement in chronometers.
The Motor-Clock, and the entire apparatus for maintaining the action of sympathetic Clocks, regulating distant clocks, distributing time-signals through the country, dropping time-signal-balls, firing time-signal-guns, &c., are in a perfectly efficient state. Of the external time-signals, the only one for which I am officially responsible is the Time-Signal-Ball at Deal; to which the galvanic communication is practically difficult. The report on the success of communication is sensibly the same as last year's; on 83·3 per cent. of days, the ball was properly dropped; on 8·2 per cent., in damp weather, the current was assisted by hand; on 4·9 per cent. no current passed; and on 3·6 per cent. the wind was too heavy to permit the raising of the ball.
On the Great Clock of Westminster Palace it will be sufficient to remark that, on 50 per cent. of days of observation its error is less than 1s, and on 96 percent. it is less than 3s.
For the clocks at the Lombard-Street Post-Office I some years ago arranged an apparatus by which at noon every day a galvanic current from this Observatory seizes the second-hand of the principal clock and turns it round (if necessary) so as to make it point to 0s. This apparatus has been long in action without a failure.
The management of the various business of Chronometers and Time-Signals occupies the entire office-time of one of my most trusted assistants and one intelligent Supernumerary Computer.
No step has been taken by the Government in reference to the establishment of hourly time-signals on the Start Point.
No determination of longitude has been made in the past year. I have desired to commemorate the most important determinations of longitude that have ever been made by the erection of a monolith pillar on the Feagh Main station in Valencia; the point from which longitude is measured eastwardly to Orsk on the frontier of Asia and westwardly to Cambridge in the United States. But the sum demanded by the Workers of the quarry was so large that I have taken no further action in this matter.
XIV.– Personal Establishment:–
The establishment of Assistants is the same as at the last Report, … Mr. Ellis is entirely occupied in the morning of every day with the business of Chronometers, Time-Signals, Galvanism, and (occasionally) Money Accounts; … All, however, as well as some of the Junior Computers, are employed in observations; those with the Equatoreal being usually confided to Mr. Carpenter.
XV.–Extraneous Work:–
Some of our time has been occupied with arrangements for time-signals by galvanic communication at Bombay and Madras; and personally I have given attention, at the request of Departments of the Government, to matters connected with the Observatories of these places.
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