Autobiography of Sir George Biddell Airy, George Biddell Airy [best english books to read for beginners txt] 📗

the mountains of Cumberland, I had remarked that a 'man' or cairn of stones erected by the Ordnance Surveyors on the Great Gable had covered up a curious natural stone trough, known as one of the remarkable singularities of the country. This year, without giving any notice to the Ordnance Surveyors, I sent two wallers from Borrowdale to the mountain top, to remove the 'man' about 10 feet and expose the trough. Sir Henry James afterwards approved of my act, and refunded the expense.--I investigated the optical condition of an eye with conical cornea.

"The Harton Colliery Experiment: I had long wished to repeat the experiment which I had attempted unsuccessfully in 1826 and 1828, of determining by pendulum-vibrations the measure of gravity at the bottom of a mine. Residing near Keswick this summer, and having the matter in my mind, I availed myself of an introduction from Dr Leitch to some gentlemen at South Shields, for inspection of the Harton Colliery. I judged that it would answer pretty well. I find that on Aug. 11th I wrote to Mr Anderson (lessee of the mine), and on the same day to the Admiralty requesting authority to employ a Greenwich Assistant, and requesting L100 for part payment of expenses. On August 16th the Admiralty assent. There were many preparations to be made, both personal and instrumental. My party consisted of Dunkin (Superintendant), Ellis, Criswick, Simmons, Pogson, and Ruemker: I did not myself attend the detail of observations. The observations began on Oct. 2nd and ended on Oct. 21st: supplementary observations were subsequently made at Greenwich for examining the coefficient of temperature-correction. On Oct. 24th I gave a Lecture at South Shields on the whole operation. In 'Punch' of Nov. 18th there was an excellent semi-comic account of the experiment, which as I afterwards found was written by Mr Percival Leigh."

Of private history: "On Jan. 18th I returned from Playford. From Mar. 10th to 13th I was at Deal, and visited Sir John Herschel at Hawkhurst.--From June 28th to Aug. 7th I was staying with my family at The Grange, in Borrowdale near Keswick: and also made an expedition to Penrith, Carlisle, Newcastle, Jarrow, &c.; and descended the Harton Pit.--In September and also in October I was at South Shields on the Harton Experiments.--From Dec. 14th to 18th I was at Cambridge, and on the 26th I went to Playford."

The following letter, written in answer to a lady who had asked him to procure permission from Lord Rosse for her to observe with his telescope, is characteristic:


ROYAL OBSERVATORY, GREENWICH.
1854, September 20 .

DEAR MADAM,

The state of things with regard to Lord Rosse's Telescope is this. If a night is fine, it is wanted for his use or for the use of professional astronomers. If it is not fine, it is of no use to anybody. Now considering this, and considering that the appropriation of the telescope on a fine night to any body but a technical astronomer is a misapplication of an enormous capital of money and intellect which is invested in this unique instrument--it is against my conscience to ask Lord Rosse to place it at the service of any person except an experienced astronomer. No introduction, I believe, is necessary for seeing it in the day-time. The instrument stands unenclosed in the Castle Demesne, to which strangers are admitted without question, I believe...............

Faithfully yours,
G.B. AIRY.


1855

"On May 9th it was notified to me (I think through the Hydrographer) that the Admiralty were not unwilling to increase my salary. I made application therefore; and on Jan. 21st 1856 Sir Charles Wood notified to me that the Admiralty consented to have it raised from L800 to
L1000 .--In the Report to the Board of Visitors it appears that 'At the instance of the Board of Trade, acting on this occasion through a Committee of the Royal Society, a model of the Transit Circle (with the improvement of perforated cube, &c. introduced in the Cape Transit Circle) has been prepared for the Great Exhibition at Paris.'--Under the head of Reduction of Astronomical Observations it is stated that '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.... 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 ear method.'--With regard to the Reduction of the Magnetical Observations, 'I have not yet felt sufficiently satisfied with any proposed method of discussing the magnetic results to devote any time to their further treatment.'--'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.--Application has been made to me from one of the important offices of Government (the Post Office) 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."--With respect to the operations for determining the longitude of Paris, it is stated that, "The whole number of days of signal transmission was eighteen, and the whole number of signals transmitted was 2530. 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 1703. Very great care was taken on both sides, for the adjustments of the instruments. The resulting difference of longitude, 9m. 20.63s., is probably very accurate. It is less by nearly 1s. of time than that determined in 1825 by rocket-signals, under the superintendance of Sir John Herschel and Col. Sabine. The time occupied by the passage of the galvanic current appears to be 1/12th of a second."--With regard to the Pendulum Experiments in the Harton Colliery, after mentioning that personal assistance had been sought and obtained from the Observatories of Cambridge, Oxford, Durham, and Red Hill, the Report states that "The experiments appear to have been in every point successful, shewing beyond doubt that gravity is increased at the depth of 1260 feet by 1/10000th part. I trust 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."--On Oct. 18th the Astronomer Royal printed an Address to the Individual Members of the Board of Visitors on the subject of a large new Equatoreal for the Observatory. After a brief statement of the existing equipment of the Observatory in respect of equatoreal instruments, the Address continues thus: "It is known to the Visitors that I have uniformly objected to any luxury of extrameridional apparatus, which would materially divert us from a steady adherence to the meridional system which both reason and tradition have engrafted on this Observatory. But I feel that our present instruments are insufficient even for my wishes; and I cannot overlook the consideration that due provision must be made for future interests, and that we are nearer by twenty years to the time when another judgment must decide on the direction which shall be given to the force of the Observatory."--"In August I had some correspondence about the Egyptian wooden astronomical tablets with Mr Gresswell and others: they were fully examined by Mr Ellis.--In this year I was much engaged on schemes for compasses, and in June I sent my Paper on Discussions of Ships' Magnetism to the Royal Society.--On Dec. 6th the mast of the Observatory time-ball broke, and the Ball fell in the Front Court.--On Aug. 4th my valued friend Mr Sheepshanks died; and on Aug. 14th I went to London to see the Standard Bars as left by him. Afterwards, on Oct. 25th I went to Reading to collect the papers about Standards left by Mr Sheepshanks.--I made a mechanical construction for Euclid I. 47, with which I was well satisfied.--On Apr. 13th I joined a deputation to the Chancellor of the Exchequer (Sir G. Cornewall Lewis) on Decimal Coinage."

Of private history: "I was at Playford for a large part of January.--On Mar, 26th I went to Reading, to visit Mr Sheepshanks, and afterwards to Silchester and Hereford.--On June 21st I went with my wife and two eldest sons to Edinburgh and other places in Scotland, but residing principally at Oban, where I hired a house. Amongst other expeditions, I and my son Wilfrid went with the 'Pharos' (Northern Lights Steamer) to the Skerry Vohr Lighthouse, &c. I also visited Newcastle, &c., and returned to Greenwich on Aug. 2nd.--From Oct. 12th to 17th I was at Cambridge.--On Dec. 24th I went to Playford."


CHAPTER VII.

AT GREENWICH OBSERVATORY--1856 TO 1866.


1856

"In the Report to the Visitors there is an interesting account of the difficulties experienced with the Reflex Zenith Tube in consequence of the tremors of the quicksilver transmitted through the ground. Attempts were made to reduce the tremor by supporting the quicksilver trough on a stage founded at a depth of 10 feet below the surface, but it was not in the smallest degree diminished, and the Report states that 'The experience of this investigation justifies me in believing that no practicable depth of trench prevents the propagation of tremor when the soil is like that of Greenwich Hill, a gravel, in all places very hard, and in some, cemented to the consistency of rock.'--With respect to the regulation of the Post Office clocks, 'One of the galvanic clocks in the Post Office Department, Lombard