Autobiography of Sir George Biddell Airy - George Biddell Airy (android based ebook reader txt) 📗

just called to invite us to dinner to-morrow.--I propose to George Arthur Biddell that he go to Newcastle this evening, in order to see glass works and other things there to-morrow, and to return when he can.

I think that I can persuade Barlow to stop to see the experiments out, and if so I shall endeavour to return as soon as possible. The earliest day would be the day after to-morrow.

* * * * *

The following extract is from a letter written to Mr Murray for insertion in his Handbook of France, relating to the Breakwater at Cherbourg, which Airy had visited during his journey in France in the autumn of this year.


ROYAL OBSERVATORY, GREENWICH,
_1845, Oct. 8th_.

My opinion on the construction I need not say ought not to be quoted: but you are quite welcome to found any general statement on it; or perhaps it may guide you in further enquiries. To make it clear, I must speak rather generally upon the subject. There are three ways in which a breakwater may be constructed. 1. By building a strong wall with perpendicular face from the bottom of the sea. 2. By making a bank with nothing but slopes towards the sea. 3. By making a sloping bank to a certain height and then building a perpendicular wall upon it.--Now if the 1st of these constructions could be arranged, I have no doubt that it would be the best of all, because a sea does not _break_ against a perpendicular face, but recoils in an unbroken swell, merely making a slow quiet push at the wall, and not making a violent impact. But practically it is nearly impossible. The 2nd construction makes the sea to break tremendously, but if the sloping surface be made of square stone put together with reasonable care there is not the smallest tendency to unseat these stones. This is the principle of construction of Plymouth Breakwater. In the 3rd construction, the slope makes the sea to break tremendously, and then it strikes the perpendicular face with the force of a battering ram: and therefore in my opinion this is the worst construction of all. A few face-stones may easily be dislodged, and then the sea entering with this enormous force will speedily destroy the whole. This is the form of the Cherbourg Digue.

From this you will gather that I have a full belief that Plymouth Breakwater will last very long, and that the Digue of Cherbourg, at least its upper wall, will not last long. The great bank will last a good while, gradually suffering degradation, but still protecting the Road pretty well.

I was assured by the officers residing on the Digue that the sea which on breaking is thrown vertically upwards and then falls down upon the pavement does sometimes push the stones about which are lying there and which weigh three or four tons.

I saw some preparations for the foundations of the fort at the eastern extremity of the Digue. One artificial stone of concrete measured 12'9" x 6'7" x 5'7", and was estimated to weigh 25000 kilogrammes.


CHAPTER VI.

AT GREENWICH OBSERVATORY--1846 TO 1856.


1846

"On Nov. 7th I proposed a change in the form of Estimates for the Observatory. The original astronomical part was provided by the Admiralty, and the new magnetical and meteorological part was provided by the Treasury: and the whole Estimates and Accounts of the Observatory never appeared in one public paper. I proposed that the whole should be placed on the Navy Estimates, but the Admiralty refused. I repeated this in subsequent years, with no success. Meantime I always sent to the Admiralty a duplicate of my Treasury Estimate with the proper Admiralty Estimate.--Stephenson's Railway through the lower part of the Park, in tunnel about 850 feet from the Observatory, was again brought forward. On Feb. 20th it was put before me by the Government, and on March 9th I made experiments at Kensal Green, specially on the effect of a tunnel: which I found to be considerable in suppressing the tremors. On May 6th I made my Report, generally favourable, supposing the railway to be in tunnel. On May 13th I, with Mr Stephenson, had an interview at the Admiralty with Lord Ellenborough and Sir George Cockburn. The Earl appeared willing to relax in his scruples about allowing a railway through the Park, when Sir George Cockburn made a most solemn protest against it, on the ground of danger to an institution of such importance as the Observatory. I have no doubt that this protest of Sir George Cockburn's really determined the Government. On June 10th I was informed that the Government refused their consent. After this the South Eastern Railway Company adopted the line through Tranquil Vale.--In consequence of the defective state of Paramatta Observatory I had written to Sir Robert Peel on April 16th raising the question of a General Superintending Board for Colonial Observatories: and on June 27th I saw Mr Gladstone at the Colonial Office to enquire about the possibility of establishing local Boards. On June 29th a general plan was settled, but it never came to anything.--Forty volumes of the Observatory MSS. were bound--an important beginning.--Deep-sunk thermometers were prepared by Prof. Forbes.--On June 22nd Sir Robert Inglis procured an Order of the House of Commons for printing a paper of Sir James South's, ostensibly on the effects of a railway passing through Greenwich Park, but really attacking almost everything that I did in the Observatory. I replied to this on July 21st by a letter in the Athenaeum addressed to Sir Robert Inglis, in terms so strong and so well supported that Sir James South was effectually silenced." The following extract from a letter of Airy's to the Earl of Rosse, dated Dec. 15th 1846, will shew how pronounced the quarrel between Airy and South had become in consequence of the above-mentioned attack and previous differences: "After the public exposure which his conduct in the last summer compelled me to make, I certainly cannot meet him on equal terms, and desire not to meet him at all." (Ed.).--"In the Mag. and Met. Department, I was constantly engaged with Mr Charles Brooke in the preparation and mounting of the self-registering instruments, and the chemical arrangements for their use, to the end of the year. With Mr Ronalds I was similarly engaged: but I had the greatest difficulty in transacting business with him, from his unpractical habits.--The equipment of the Liverpool Observatory, under me, was still going on: I introduced the use of Siemens's Chronometric Governor for giving horary motion to an Equatoreal there. I have since introduced the same principle in the Chronograph Barrel and the Great Equatoreal at Greenwich: I consider it important.--On Feb. 13th I received the Astronomical Society's Medal for the Planetary Reductions.--In the University of London: At this time seriously began the discussion whether there should be a compulsory examination in matters bearing on religious subjects. After this there was no peace.--For discovery of Comets three medals were awarded by Schumacher and me: one to Peters, two to De Vico. A comet was seen by Hind, and by no other observer: after correspondence, principally in 1848, the medal was refused to him.--With respect to the Railway Gauge Commission: On Jan. 1st, in our experiments near York, the engine ran off the rails. On Jan. 29th the Commissioners signed the Report, and the business was concluded by the end of April. Our recommendation was that the narrow gauge should be carried throughout. This was opposed most violently by partisans of the broad gauge, and they had sufficient influence in Parliament to prevent our recommendation from being carried into effect. But the policy, even of the Great Western Railway (in which the broad gauge originated), has supported our views: the narrow gauge has been gradually substituted for the broad: and the broad now (1872) scarcely exists.--On June 20th Lord Canning enquired of me about makers for the clock in the Clock Tower of Westminster Palace. I suggested Vulliamy, Dent, Whitehurst; and made other suggestions: I had some correspondence with E. B. Denison, about clocks.--I had much correspondence with Stephenson about the Tubular Bridge over the Menai Straits. Stephenson afterwards spoke of my assistance as having much supported him in this anxious work: on Dec. 11th I was requested to make a Report, and to charge a fee as a Civil Engineer; but I declined to do so. In January I went, with George Arthur Biddell, to Portsmouth, to examine Lord Dundonald's rotary engine as mounted in the 'Janus,' and made a Report on the same to the Admiralty: and I made several subsequent Reports on the same matter. The scheme was abandoned in the course of next year; the real cause of failure, as I believe, was in the bad mounting in the ship.

"The engrossing subject of this year was the discovery of Neptune. As I have said (1845) I obtained no answer from Adams to a letter of enquiry. Beginning with June 26th of 1846 I had correspondence of a satisfactory character with Le Verrier, who had taken up the subject of the disturbance of Uranus, and arrived at conclusions not very different from those of Adams. I wrote from Ely on July 9th to Challis, begging him, as in possession of the largest telescope in England, to sweep for the planet, and suggesting a plan. I received information of its recognition by Galle, when I was visiting Hansen at Gotha. For further official history, see my communications to the Royal Astronomical Society, and for private history see the papers in the Royal Observatory. I was abused most savagely both by English and French."

The Report to the Visitors contains an interesting account of the Great Lunar Reductions, from which the following passage is extracted: "Of the Third Section, containing the comparison of Observed Places with Tabular Places, three sheets are printed, from 1750 to 1756. This comparison, it is to be observed, does not contain a simple comparison of places, but contains also the coefficients of the various changes in the moon's place depending on changes in the elements.... The process for the correction of the elements by means of these comparisons is now going on: and the extent of this work, even after so much has been prepared, almost exceeds belief. For the longitude, ten columns are added in groups, formed in thirteen different ways, each different way having on the average about nine hundred groups. For the ecliptic polar distance, five columns are added in groups, formed in seven different ways, each different way having on the average about nine