Of private history: There was the usual winter visit to Playford.--In April he made a short trip to Cornwall with his daughter Annot.--In June he was appointed a Companion of the Bath, and was presented at Court on his appointment.--Mrs Airy was staying with her daughter, Mrs Routh, at Hunstanton, during June, her state of health being somewhat improved.--From August 1st to 28th he was chiefly in c.u.mberland, at Barrow House, and at Grange, Borrowdale, where his son Osmund was staying for a holiday.

1872

"From the Report to the Board of Visitors it appears that 'The Normal Siderial Clock for giving sidereal time by galvanic communication to the Astronomical Observatory was established in the Magnetic Bas.e.m.e.nt in 1871, June; that locality being adapted for it on account of the uniformity of temperature, the daily changed of temperature rarely exceeding 1 Fahrenheit. Its escapement is one which I suggested many years ago in the Cambridge Transactions; a detached escapement, very closely a.n.a.logous to the ordinary chronometer escapement, the pendulum receiving an impulse only at alternate vibrations.... The steadiness of rate is very far superior to any that we have previously attained.'--The aspect of railway enterprise is at present favourable to the Park and to the Observatory. The South-Eastern Railway Company has made an arrangement with the Metropolitan Board of Works for shifting the course of the great Southern Outfall Sewer. This enables the Company to trace a new line for the railway, pa.s.sing on the north side of London Street, at such a distance from the Observatory as to remove all cause of alarm. I understand that the Bill, which was unopposed, has pa.s.sed the Committee of the House of Commons. I trust that the contest, which has lasted thirty-seven years, is now terminated.--The observations of 7 Draconis with the Water-Telescope, made in the autumn of 1871, and the spring of 1872, are reduced, the latter only in their first steps.... Using the values of the level scales as determined by Mr Simms (which I have no reason to believe to be inaccurate) the spring and autumn observations of 1871 absolutely negative the idea of any effect being produced on the constant of aberration by the amount of refracting medium traversed by the light.--The great Aurora of 1872 Feb. 4 was well observed. On this occasion the term Borealis would have been a misnomer, for the phenomenon began in the South and was most conspicuous in the South. Three times in the evening it exhibited that umbrella-like appearance which has been called (perhaps inaccurately) a corona. I have very carefully compared its momentary phenomena with the corresponding movements of the magnetometers. In some of the most critical times, the comparison fails on account of the violent movements and consequent faint traces of the magnetometers. I have not been able to connect the phases of aurora and those of magnetic disturbance very distinctly.--The Report contains a detailed account of the heavy preparations for the observation of the Transit of Venus 1874, including the portable buildings for the instruments, the instruments themselves (being a transit-instrument, an altazimuth, and an equatoreal, for each station), and first cla.s.s and second-cla.s.s clocks, all sufficient for the equipment of 5 stations, and continues thus: I was made aware of the a.s.sent of the Government to the wish of the Board of Visitors, as expressed at their last meeting, that provision should be made for the application of photography to the observation of the Transit of Venus. It is unnecessary for me to remark that our hope of success is founded entirely on our confidence in Mr De La Rue. Under his direction, Mr Dallmeyer has advanced far in the preparation of five photoheliographs.... The subject is recognized by many astronomers as not wholly free from difficulties, but it is generally believed that these difficulties may be overcome, and Mr De La Rue is giving careful attention to the most important of them.--I take this opportunity of reporting to the Board that the Observatory was honoured by a visit of His Majesty the Emperor of Brazil, who minutely examined every part."--After referring to various subjects which in his opinion might be usefully pursued systematically at the Observatory, the Report proceeds thus: "'The character of the Observatory would be somewhat changed by this innovation, but not, as I imagine, in a direction to which any objection can be made. It would become, pro tanto, a physical observatory; and possibly in time its operations might be extended still further in a physical direction.'--The consideration of possible changes in the future of the Observatory leads me to the recollection of actual changes in the past. In my Annual Reports to the Visitors I have endeavoured to chronicle these; but still there will be many circ.u.mstances which at present are known only to myself, but which ought not to be beyond the reach of history. I have therefore lately employed some time in drawing up a series of skeleton annals of the Observatory (which unavoidably partakes in some measure of the form of biography), and have carried it through the critical period, 1836-1851. If I should command sufficient leisure to bring it down to 1861, I think that I might then very well stop." (The skeleton annals here referred to are undoubtedly the ma.n.u.script notes which form the basis of the present biography. Ed.)--"On Feb. 23rd in this year I first (privately) formed the notion of preparing a numerical Lunar Theory by subst.i.tuting Delaunay's numbers in the proper Equations and seeing what would come of it."

Of private history: There was the usual visit to Playford--in this year later than usual--from Feb. 4th to Mar. 4th. The letters written during this visit are, as usual, full of freshness and delight at finding himself in his favourite country village.--On June 5th he went to Barrow House, near Keswick, to be present at the marriage of his second son Hubert to Miss S. C. Langton, daughter of Z. Langton Esq., of Barrow House.--After the wedding he made a trip through the Trossachs district of Scotland with his daughter Annot, and returned to Greenwich on June 17th.

On the 26th June 1872 Airy was appointed a Knight Commander of the Most Honourable Order of the Bath: he was knighted by the Queen at Osborne on the 30th of July. In the course of his official career he had three times been offered Knighthood, and had each time declined it: but it seemed now as if his scruples on the subject were removed, and it is probable that he felt gratified by the public recognition of his services. Of course the occasion produced many letters of congratulation from his friends: to one of these he replied as follows: "The real charm of these public compliments seems to be, that they excite the sympathies and elicit the kind expressions of private friends or of official superiors as well as subordinates. In every way I have derived pleasure from these." From the a.s.sistants of the Royal Observatory he received a hearty letter of congratulation containing the following paragraph. "Our position has naturally given us peculiar opportunities for perceiving the high and broad purposes which have characterized your many and great undertakings, and of witnessing the untiring zeal and self-denial with which they have been pursued."

On the 18th of March 1872 Airy was nominated a Foreign a.s.sociate of the Inst.i.tut de France, to fill the place vacant by the death of Sir John Herschel. The following letter of acknowledgment shews how much he was gratified by this high scientific honour:

ROYAL OBSERVATORY, GREENWICH, _1872, March 23_.

_a_ Messieurs Messieurs ELIE DE BEAUMONT, _et_ J.B. DUMAS, _Secretaires perpetuels de l'Academie des Sciences, Inst.i.tut de France._

GENTLEMEN,

I am honoured with your letter of March 18, communicating to me my nomination by the Academy of Sciences to the place rendered vacant in the cla.s.s of Foreign a.s.sociates of the Academy by the decease of Sir John Herschel, and enclosing Copy of the Decree of the President of the French Republic approving the Election.

It is almost unnecessary for me to attempt to express to you the pride and gratification with which I receive this announcement. By universal consent, the t.i.tle of _a.s.socie Etranger de l'Academie des Sciences_ is recognised as the highest distinction to which any man of science can aspire; and I can scarcely imagine that, unless by the flattering interpretation of my friends in the Academy, I am ent.i.tled to bear it. But in any case, I am delighted to feel that the bands of friendship are drawn closer between myself and the distinguished body whom, partly by personal intercourse, partly by correspondence, and in every instance by reputation, I have known so long.

I beg that you will convey to the Academy my long-felt esteem for that body in its scientific capacity, and my deep recognition of its friendship to me and of the honor which it has conferred on me in the late election.

I have the honor to be Gentlemen, Your very faithful servant, G.B. AIRY.

On the 20th November 1872 Airy was nominated a Grand Cross in the Imperial Order of the Rose of Brazil: the insignia of the Order were accompanied by an autograph letter from the Emperor of Brazil, of which the following is a transcript.

MONSIEUR,

Vous etes un des doyens de la science, et le President de l'ill.u.s.tre Societe, qui a eu la bienveillance d'inscrire mon nom parmi ceux de ses a.s.socies. La maniere, dont vous m'avez fait les honneurs de votre Observatoire m'a impose aussi l'agreable devoir d'indiquer votre nom a l'empereur de Bresil pour un temoignage de haute estime, dont je suis fort heureux de vous faire part personellement, en vous envoyant les decorations que vous garderez, an moins, comme un souvenir de ma visite a Greenwich.

J'espere que vous m'informerez, quand il vous sera aise, des travaux de votre observatoire, et surtout de ce que l'on aura fait pour l'observation du pa.s.sage de Venus et la determination exacte de la pa.s.sage.

J'ai recu deja les _Proceedings de la Royal Society_ lesquels m'interessent vivement.

Je voudrais vous ecrire dans votre langue, mais, comme je n'en ai pas l'habitude, j'ai craigne de ne pas vous exprimer tout-a-fait les sentiments de

Votre affectionne, D. PEDRO D'ALCANTARA.

RIO, _22 Octobre, 1872_.

Airy's reply was as follows:

ROYAL OBSERVATORY, GREENWICH, _1872, November 26_.

SIRE,

I am honoured with your Imperial Majesty's autograph letter of October 22 informing me that, on considering the attention which the Royal Society of London had been able to offer to your Majesty, as well as the explanation of the various parts of the establishment of this Observatory which I had the honor and the high gratification to communicate, You had been pleased to place my name in the Imperial Order of the Rose, and to present to me the Decorations of Grand Cross of that Order.

With pride I receive this proof of Your Majesty's recollection of your visit to the scientific inst.i.tutions of Great Britain.

The Diploma of the appointment to the Order of the Rose, under the Imperial Sign Manual, together with the Decorations of the Order, have been transmitted to me by his Excellency Don Pereira de Andrada, Your Majesty's Representative at the British Court.

Your Majesty has been pleased to advert to the approaching Transit of Venus, on the preparations for which you found me engaged. It is unfortunate that the Transit of 1874 will not be visible at Rio de Janeiro. For that of 1882, Rio will be a favourable position, and we reckon on the observations to be made there. Your Majesty may be a.s.sured that I shall loyally bear in mind your desire to be informed of any remarkable enterprise of this Observatory, or of any princ.i.p.al step in the preparations for the Transit of Venus and of its results.

I have the honor to be Sire, Your Imperial Majesty's very faithful servant, G.B. AIRY.

_To His Majesty The Emperor of Brazil._

Airy's old friend, Adam Sedgwick, was now very aged and infirm, but his spirit was still vigorous, and he was warm-hearted as ever. The following letter from him (probably the last of their long correspondence) was written in this year, and appears characteristic:

TRINITY COLLEGE, CAMBRIDGE, _May 10, 1872_.

MY DEAR AIRY,

I have received your card of invitation for the 1st of June, and with great joy should I count upon that day if I thought that I should be able to accept your invitation: but alas I have no hope of the kind, for that humiliating malady which now has fastened upon me for a full year and a half has not let go its hold, nor is it likely to do so. A man who is journeying in the 88th year of his pilgrimage is not likely to throw off such a chronic malady. Indeed were I well enough to come I am deaf as a post and half blind, and if I were with you I should only be able to play dummy. Several years have pa.s.sed away since I was last at your Visitation and I had great joy in seeing Mrs Airy and some lady friends at the Observatory, but I could not then attend the dinner. At that Meeting were many faces that I knew, but strangely altered by the rude handling of old Time, and there were many new faces which I had never seen before at a Royal Society Meeting; but worse than all, all the old faces were away. In vain I looked round for Wollaston, Davy, Davies Gilbert, Barrow, Troughton, &c. &c.; and the merry companion Admiral Smyth was also away, so that my last visit had its sorrowful side. But why should I bother you with these old man's mopings.

I send an old man's blessing and an old man's love to all the members of your family; especially to Mrs Airy, the oldest and dearest of my lady friends.

I remain, my dear Airy, Your true-hearted old friend, his ADAM X SEDGWICK.

mark

P.S. Shall I ever again gaze with wonder and delight from the great window of your Observatory.

The body of the above letter is in the handwriting of an amanuensis, but the signature and Postscript are in Sedgwick's handwriting. (Ed.)

1873

"Chronographic registration having been established at the Paris Observatory, Mr Hilgard, princ.i.p.al officer of the American Coast Survey, has made use of it for determining the longitude of Harvard from Greenwich, through Paris, Brest, and St Pierre. For this purpose Mr Hilgard's Transit Instrument was planted in the Magnetic Court. I understand that the result does not sensibly differ from that obtained by Mr Gould, through Valentia and Newfoundland.--It was known to the scientific world that several of the original thermometers, constructed by Mr Sheepshanks (in the course of his preparation of the National Standard of Length) by independent calibration of the bores, and independent determination of the freezing and boiling points on arbitrary graduations, were still preserved at the Royal Observatory.

It was lately stated to me by M. Tresca, the princ.i.p.al officer of the International Metrical Commission, that, in the late unhappy war in Paris, the French original thermometers were destroyed; and M. Tresca requested that, if possible, some of the original thermometers made by Mr Sheepshanks might be appropriated to the use of the International Commission. I have therefore transferred to M. Tresca the three thermometers A.6, S.1, S.2, with the doc.u.mentary information relating to them, which was found in Mr Sheepshanks's papers; retaining six thermometers of the same cla.s.s in the Royal Observatory.--The Sidereal Standard Clock continues to give great satisfaction. I am considering (with the aid of Mr Buckney, of the firm of E. Dent and Co.) an arrangement for barometric correction, founded on the principle of action on the pendulum by means of a magnet which can be raised or lowered by the agency of a large barometer.--The Altazimuth has received some important alterations. An examination of the results of observations had made me dissatisfied with the bearings of the horizontal pivots in their Y's. Mr Simms, at my request, changed the bearings in Y's for bearing in segments of circles, a construction which has worked admirably well in the pivots of the Transit Circle."

(And in various other respects the instrument appears to have received a thorough overhauling. Ed.)--"With the consent of the Royal Society and of the Kew Committee, the Kew Heliograph has been planted in the new dome looking over the South Ground. It is not yet finally adjusted.--Some magnetic observations in the Britannia and Conway tubular bridges were made last autumn. For this purpose I detached an a.s.sistant (Mr Carpenter), who was aided by Capt. Tupman, R.M.A.; in other respects the enterprise was private and at private expense.--The rates of the first six chronometers (in the annual trials) are published, in a form which appears most likely to lead to examination of the causes that influence their merits or demerits. This report is extensively distributed to British and Foreign horologists and instrument-makers. All these artists appear to entertain the conviction that the careful comparisons made at this Observatory, and the orderly form of their publication, have contributed powerfully to the improvement of chronometers.--Very lately, application has been made to me, through the Board of Trade, for plans and other information regarding time-signal-b.a.l.l.s, to a.s.sist in guiding the authorities of the German Empire in the establishment of time signals at various ports of that State. In other foreign countries the system is extending, and is referred to Greenwich as its origin.--The arrangements and preparations for the observation of the Transit of Venus occupied much attention. With regard to the photoheliographs it is proposed to make trial of a plan proposed by M. Janssen, for numerous photographs of Venus when very near to the Sun's limb. On Apr. 26th the engaging of photographic teachers was sanctioned.

Observers were selected and engaged. A working model of the Transit was prepared, and the use of De La Rue's Scale was practised. There was some hostile criticism of the stations selected for the observation of the Transit, which necessitated a formal reply.--Reference is made to the increase of facilities for making magnetical and meteorological observations. The inevitable result of it is, that observations are produced in numbers so great that complete reduction becomes almost impossible. The labour of reduction is very great, and it is concluded that, of the enormous number of meteorological observations now made at numerous observatories, very few can ever possess the smallest utility.--Referring to my Numerical Lunar Theory: on June 30th, 1873, a theory was formed, nearly but not perfectly complete. Numerical development of powers of ar and ra. Factors of corrections to Delaunay first attempted, but entirely in numerical form."--In March of this year Airy was consulted by Mr W.H. Barlow, C.E., and Mr Thomas Bouch (the Engineer of the Tay Bridge, which was blown down in 1879, and of a proposed scheme for a Forth Bridge in 1873) on the subject of the wind pressure, &c., that should be allowed for in the construction of the bridge. Airy's report on this question is dated 1873, Apr. 9th: it was subsequently much referred to at the Official Enquiry into the causes of the failure of the Tay Bridge.--At the end of this year Airy resigned the Presidency of the Royal Society. In his Address to the Society on Dec. 1st he stated his reasons in full, as follows: "the severity of official duties, which seem to increase, while vigour to discharge them does not increase; and the distance of my residence.... Another cause is a difficulty of hearing, which unfits me for effective action as Chairman of Council."