"In brief revision of the years from 1827 to 1835 I may confine myself to the two princ.i.p.al subjects--my Professorial Lectures, and my Conduct of the Cambridge Observatory.

"The Lectures as begun in 1827 included ordinary Mechanics, ordinary Hydrostatics and Pneumatics (I think that I did not touch, or touched very lightly, on the subjects connected with the Hydraulic Ram), and ordinary Optics (with a very few words on Polarization and Depolarization). In 1828 the two first were generally improved, and for the third (Optics) I introduced a few words on Circular Polarization. I believe that it was in 1829 that I made an addition to the Syllabus with a small engraving, shewing the interference of light in the best practical experiment (that of the flat prism); and I went thoroughly into the main points of the Undulatory Theory, interference, diffraction, &c. In 1830 I believe I went (in addition to what is mentioned above) into Polarization and Depolarization of all kinds. My best lecture diagrams were drawn and painted by my wife. The Lectures were universally p.r.o.nounced to be valuable. The subjects underwent no material change in 1831, 2, 3, 4, 5; and I believe it was a matter of sincere regret to many persons that my removal to Greenwich terminated the series. Each lecture nominally occupied an hour. But I always encouraged students to stop and talk with me; and this supplement was usually considered a valuable part of the lecture. Practically the lecture, on most days, occupied two hours. I enjoyed the Lectures much: yet I felt that the labour (in addition to other work) made an impression on my strength, and I became at length desirous of terminating them.

"The Observatory, when I took charge of it, had only one instrument--the Transit-Instrument The principles however which I laid down for my own direction were adapted to the expected complete equipment, Planets (totally neglected at Greenwich) were to be observed. Observations were to be reduced completely, and the reductions were to be exhibited in an orderly way: this was a novelty in Astronomy. I considered it so important that I actually proposed to omit in my publication the original observations, but was dissuaded by Herschel and others. I sometimes suspended, observations for a short time, in order to obtain leisure for; the reductions. I had at first no intention of correcting the places of the fundamental stars as settled at Greenwich. But I found myself compelled to do so, because they were not sufficiently accurate; and then I took the course of observing and reducing as an independent observer, without reference to any other observatory. I introduced the principle of not correcting instrumental errors, but measuring them and applying numerical corrections. I determined my longitude by chronometers, and my lat.i.tude by a repeating circle borrowed from Mr Sheepshanks, which I used so well that the result; was only half a second in error. The form of my reductions in the published volume for 1828 is rather irregular, but the matter is good: it soon attracted attention. In 1829 the process was much the same: I had an a.s.sistant, Mr Baldrey.

In 1830 still the same, with the additions:--that I formally gave the corrections of relative right-ascension of fundamental stars (without alteration of equinox, which I had not the means of obtaining) to be used in the year 1831; and that I reduced completely the observed occultations (with a small error, subsequently corrected). In 1831 the system of correction of broken transits was improved: the errors of a.s.sumed R.A. of Fundamental Stars were exhibited: Mean Solar Time was obtained from Sidereal Time by time of Transit of [Symbol: Aries]

(computed by myself): the method of computing occultations was improved. In 1832 the small Equatoreal was erected, and was soon employed in observations of the elongation of the 4th Satellite of Jupiter for determining the ma.s.s of Jupiter. The Mural Circle was erected at the end of the year, but not used. The calculation of R.A. of Fundamental Stars was made h.o.m.ogeneously with the others: separate results of all were included in ledgers: a star-catalogue was formed: all as to the present time (1871). With the Equatoreal the difference of N.P.D. of Mars and stars was observed.

"With the beginning of 1833 the Mural Circle was established at work, a second a.s.sistant (Mr Glaisher) was appointed, and the Observatory might be considered complete. I made experiments on the graduations of the Circle. I detected and was annoyed by the R--D. I determined the lat.i.tude. I exhibited the separate results for N.P.D. of stars in ledger, and their means in Catalogue. I investigated from my observations the place of equinox and the obliquity of the ecliptic.

I made another series of observations of Jupiter's 4th Satellite, for the ma.s.s of Jupiter. I observed the solar eclipse with the Equatoreal, by a method then first introduced, which I have since used several times at Cambridge and Greenwich with excellent effect. The Moon and the Planets were usually observed till near two in the morning.

Correction for defective illumination applied when necessary.

The volume is very complete, the only deficiency being in the observation of Moon and Planets through the severe morning hours. In 1834 the only novelties are--examination of the graduations of the declination circle of the Equatoreal (excessively bad): observations of a spot on Jupiter for rotation, and of Mars and stars. In 1835 (including January 1836) there is a more complete examination of the Equatoreal graduations: parallax and refraction for Equatoreal observations: a spot on Jupiter: a series of observations on Jupiter's 4th Satellite for the ma.s.s of Jupiter: Mars and stars: Halley's Comet (the best series of observations which could be made in the season): and a short series of meteorological observations, on a plan suggested by Sir John Herschel then at the Cape of Good Hope.

"I cannot tell precisely in which year I introduced the following useful custom. Towards the end of each year I procured a pocket-book for the following year with a s.p.a.ce for every day, and carefully examining all the sources of elements of observations, and determining the observations to be made every day, I inserted them in the pocket-book. This system gave wonderful steadiness to the plan of observations for the next year. The system has been maintained in great perfection at the Observatory of Greenwich. (The first of these pocket-books which Prof. Adams has found is that for 1833.) Printed skeleton forms were introduced for all calculations from 1828. In the Greenwich Observatory Library there is a collection, I believe complete, of printed papers commencing with my manifesto, and containing all Syndicate Reports except for 1833 (when perhaps there was none). It seems from these that my first written Report on Observations, &c., was on May 30th, 1834. The first Syndicate Report is on May 25th, 1829."

A few remarks on Airy's private life and friends during his residence at Cambridge Observatory may be here appropriately inserted.

Amid the laborious occupations recorded in the foregoing pages, his social life and surroundings appear to have been most pleasant and congenial. At that period there were in residence in Cambridge, and particularly at Trinity, a large number of very brilliant men. Airy was essentially a Cambridge man. He had come up poor and friendless: he had gained friends and fame at the University, and his whole work had been done there. From the frequent references in after times both by him and his wife to their life at Cambridge, it is clear that they had a very pleasant recollection of it, and that the social gatherings there were remarkably attractive. He has himself recorded that with Whewell and Sedgwick, and his accomplished sisters-in-law, who were frequently on long visits at the Observatory, they formed pretty nearly one family.

His friendship with Whewell was very close. Although Whewell was at times hasty, and rough-mannered, and even extremely rude, yet he was generous and large-minded, and thoroughly upright. [Footnote: The following pa.s.sage occurs in a letter from Airy to his wife, dated 1845, Sept. 17th: "I am sorry that ---- speaks in such terms of the 'Grand Master,' as she used to be so proud of him: it is only those who have _well_ gone through the ordeal of quarrels with him and almost insults from him, like Sheepshanks and me, that thoroughly appreciate the good that is in him: I am sure he will never want a good word from me."] In power of mind, in pursuits, and interests, Airy had more in common with Whewell than with any other of his friends. It was with Whewell that he undertook the experiments at Dolcoath: it was to Whewell that he first communicated the result of his remarkable investigation of the Long Inequality of Venus and the Earth; and some of his Optical researches were conducted jointly with Whewell. Whewell took his degree in 1816, seven years before Airy, and his reputation, both for mathematical and all-round knowledge, was extremely and deservedly great, but he was always most generous in his recognition of Airy's powers. Thus in a letter of Mar. 16th, 1823 (Life of William Whewell by Mrs Stair Douglas), he says, "Airy is certainly a most extraordinary man, and deserves everything that can be said of him"; and again in the autumn of 1826 he writes to his aunt, "You mentioned a difficulty which had occurred to you in one of your late letters; how Airy should be made Professor while I was here, who, being your nephew, must of course, on that account, deserve it better than he could. Now it is a thing which you will think odd, but it is nevertheless true, that Airy is a better mathematician than your nephew, and has moreover been much more employed of late in such studies.... Seriously speaking, Airy is by very much the best person they could have chosen for the situation, and few things have given me so much pleasure as his election." How much Whewell depended upon his friends at the Observatory may be gathered from a letter which he wrote to his sister on Dec. 21st, 1833. "We have lately been in alarm here on the subject of illness. Two very near friends of mine, Prof. and Mrs Airy, have had the scarlet fever at the same time; she more slightly, he very severely. They are now, I am thankful to say, doing well and recovering rapidly. You will recollect that I was staying with them at her father's in Derbyshire in the summer. They are, I think, two of the most admirable and delightful persons that the world contains." And again on Dec. 20th, 1835, he wrote to his sister Ann, "My friends--I may almost say my dearest friends --Professor Airy and his family have left Cambridge, he being appointed Astronomer Royal at Greenwich--to me an irreparable loss; but I shall probably go and see how they look in their new abode."

Their close intercourse was naturally interrupted by Airy's removal to Greenwich, but their friendly feelings and mutual respect continued without material break till Whewell's death. There was frequent correspondence between them, especially on matters connected with the conduct and teaching of the University, in which they both took a keen interest, and a warm welcome at Trinity Lodge always awaited Mr and Mrs Airy when they visited Cambridge. In a letter written to Mrs Stair Douglas on Feb. 11th, 1882, enclosing some of Whewell's letters, there occurs the following pa.s.sage: "After the decease of Mrs Whewell, Whewell wrote to my wife a mournful letter, telling her of his melancholy state, and asking her to visit him at the Lodge for a few days. And she did go, and did the honours of the house for several days. You will gather from this the relation in which the families stood." Whewell died on Mar. 6th, 1866, from the effects of a fall from his horse, and the following extract is from a letter written by Airy to Whewell's niece, Mrs Sumner Gibson, on hearing of the death of his old friend:

"The Master was, I believe, my oldest surviving friend (beyond my own family), and, after an acquaintance of 46 years, I must have been one of his oldest friends. We have during that time been connected privately and officially: we travelled together and experimented together: and as opportunity served (but I need not say in very different degrees) we both laboured for our College and University. A terrible blank is left on my mind."

Sedgwick was probably 15 years older than Airy: he took his degree in 1808. But the astonishing buoyancy of spirits and bonhomie of Sedgwick fitted him for all ages alike. He was undoubtedly the most popular man in Cambridge in modern times. His ability, his brightness and wit, his fearless honesty and uprightness, his plain-speaking and good humour, rendered him a universal favourite. His close alliance with Airy was much more social than scientific. It is true that they made some geological excursions together, but, at any rate with Airy, it was far more by way of recreation than of serious study, and Sedgwick's science was entirely geological. Their friendship continued till Sedgwick's death, though it was once or twice imperilled by Sedgwick's impulsive and hasty nature.

Peac.o.c.k took his degree in 1813 (Herschel's year), and was therefore probably 10 years older than Airy. He was the earliest and staunchest friend of Airy in his undergraduate years, encouraged him in every possible way, lent him books, a.s.sisted him in his studies, helped him with wise advice on many occasions, and took the greatest interest in his success. He was a good and advanced mathematician, and with a great deal of shrewdness and common-sense he united a singular kindness and gentleness of manner. It is therefore not to be wondered at that he was regarded by Airy with the greatest esteem and affection, and though they were afterwards separated, by Peac.o.c.k becoming Dean of Ely and Airy Astronomer Royal, yet their warm friendship was never broken. The following letter, written by Airy to Mrs Peac.o.c.k on receiving the news of the death of the Dean, well expresses his feelings towards his old friend:

TRINITY LODGE, CAMBRIDGE, _1858, Dec. 4_.

MY DEAR MADAM,

I have desired for some time to express to you my sympathies on occasion of the sad bereavement which has come upon me perhaps as strongly as upon any one not connected by family ties with my late friend. But I can scarcely give you an idea how every disposable moment of my time has been occupied. I am now called to Cambridge on business, and I seize the first free time to write to you.

My late friend was the first person whom I knew in College (I had an introduction to him when I went up as freshman). From the first, he desired me to consider the introduction not as ent.i.tling me to a mere formal recognition from him, but as authorizing me at all times to call on him for any a.s.sistance which I might require. And this was fully carried out: I referred to him in every difficulty: I had the entire command of his rooms and library (a very important aid in following the new course of mathematics which he had been so instrumental in introducing into the University) in his occasional absences: and in all respects I looked to him as to a parent. All my debts to other friends in the University added together are not comparable to what I owe to the late Dean.

Latterly I need not say that I owed much to him and that I owe much to you for your kind notice of my two sons, even since the sad event which has put it out of his power to do more.

In the past summer, looking to my custom of making a visit to Cambridge in some part of the October Term, I had determined that a visit to Ely this year should not depend on the chance of being free to leave Cambridge, but that, if it should be found convenient to yourself and the Dean, the first journey should be made to Ely. I wish that I had formed the same resolution one or two years ago.

With many thanks for your kindness, and with deep sympathy on this occasion,

I am, My dear Madam, Yours very faithfully, G.B. AIRY.

Sheepshanks was a Fellow of Trinity, in orders: he was probably seven years older than Airy (he took his degree in 1816). He was not one of Airy's earliest friends, but he had a great taste and liking for astronomy, and the friendship between them when once established became very close. He was a very staunch and fearless friend, an able and incisive writer, and remarkably energetic and diligent in astronomical investigations. He, or his sister, Miss Sheepshanks, had a house in London, and Sheepshanks was very much in London, and busied himself extremely with the work of the Royal Observatory, that of the Board of Longitude, and miscellaneous astronomical matters. He was most hospitable to his friends, and while Airy resided at Cambridge his house was always open to receive him on his frequent visits to town. In the various polemical discussions on scientific matters in which Airy was engaged, Sheepshanks was an invaluable ally, and after Airy's removal to Greenwich had more or less separated him from his Cambridge friends, Sheepshanks was still a.s.sociated with him and took a keen interest in his Greenwich work. And this continued till Sheepshanks's death. The warmest friendship always subsisted between the family at the Observatory and Mr and Miss Sheepshanks.

There were many other friends, able and talented men, but these four were the chief, and it is curious to note that they were all much older than Airy. It would seem as if Airy's knowledge had matured in so remarkable a manner, and the original work that he produced was so brilliant and copious, that by common consent he ranked with men who were much his seniors: and the natural gravity and decorum of his manners when quite a young man well supported the idea of an age considerably greater than was actually the case.

CHAPTER V.

AT GREENWICH OBSERVATORY--1836 TO 1846.

1836

"Through the last quarter of 1835 I had kept everything going on at the Greenwich Observatory in the same manner in which Mr Pond had carried it on. With the beginning of 1836 my new system began. I had already prepared 30 printed skeleton forms (a system totally unknown to Mr Pond) which were now brought into use. And, having seen the utility of the Copying Press in merchants' offices, I procured one. From this time my correspondence, public and private, is exceedingly perfect.

"At this time the dwelling house was still unconnected with the Observatory. It had no staircase to the Octagon Room. Four new rooms had been built for me on the western side of the dwelling house, but they were not yet habitable. The North-east Dome ground floor was still a pa.s.sage room. The North Terrace was the official pa.s.sage to the North-west Dome, where there was a miserable Equatoreal, and to the 25-foot Zenith Tube (in a square tower like a steeple, which connected the N.W. Dome with Flamsteed's house). The southern boundary of the garden ran down a hollow which divides the peninsula from the site of the present Magnetic Observatory, in such a manner that the princ.i.p.al part of the garden was fully exposed to the public. The Computing Room was a most pitiful little room. There was so little room for me that I transported the princ.i.p.al table to a room in my house, where I conducted much of my own official business. A large useless reflecting telescope (Ramage's), on the plan and nearly of the size of Sir W. Herschel's princ.i.p.al telescope, enc.u.mbered the centre of the Front Court.

"On Jan. 11th I addressed Mr Buck, agent of the Princess Sophia of Gloucester, Ranger of Greenwich Park, for leave to enclose a portion of the ground overlooking my garden. This was soon granted, and I was partially delivered from the inconvenience of the public gaze. The liberation was not complete till the Magnetic ground was enclosed in 1837.

"In the inferior departments of the Admiralty, especially in the Hydrographic Office (then represented by Captain Beaufort) with which I was princ.i.p.ally connected, the Observatory was considered rather as a place for managing Government chronometers than as a place of science. The preceding First a.s.sistant (Taylor) had kept a book of letter references, and I found that out of 840 letters, 820 related to Government chronometers only. On Jan. 17th I mentally sketched my regulations for my own share in chronometer business. I had some correspondence with Captain Beaufort, but we could not agree, and the matter was referred to the Admiralty. Finally arrangements were made which put the chronometer business in proper subordination to the scientific charge of the Observatory.

"In my first negociations with the Admiralty referring to acceptance of the office of Astronomer Royal, in 1834, Lord Auckland being then First Lord of the Admiralty, I had stipulated that, as my successor at Cambridge would be unprepared to carry on my Lectures, I should have permission to give a final course of Lectures there. At the end of 1835 Lord Auckland was succeeded by Lord Minto: I claimed the permission from him and he refused it. When this was known in Cambridge a pet.i.tion was presented by many Cambridge residents, and Lord Minto yielded. On April 18th I went to Cambridge with my wife, residing at the Bull Inn, and began Lectures on April 21st: they continued (apparently) to May 27th. My lecture-room was crowded (the number of names was 110) and the lectures gave great satisfaction. I offered to the Admiralty to put all the profits in their hands, and transmitted a cheque to the Accountant General of the Navy: but the Admiralty declined to receive them.

"On June 4th the Annual Visitation of the Observatory was held, Mr F. Baily in the Chair. I presented a written Report on the Observatory (a custom which I had introduced at Cambridge) in which I did not suppress the expression of my feelings about chronometer business. The Hydrographer, Captain Beaufort, who was one of the Official Visitors, was irritated: and by his influence the Report was not printed. I kept it and succeeding Reports safe for three years, and then the Board of Visitors agreed to print them; and four Reports were printed together, and bound with the Greenwich Observations of 1838.

"In the course of this year I completed the volume of Observations made at Cambridge Observatory in 1835 and on Nov. 10th the printed copies were distributed. About the end of 1835 the Dome for the Northumberland Telescope was erected: but apparently the polar frame was not erected."

The following account of an accident which occurred during the construction of the dome is extracted from a letter by Airy to his wife dated 1836 Jan. 31st. "The workmen's account of the dome blowing off is very curious: it must have been a strange gust. It started suddenly when the men were all inside and Beaumont was looking up at it: the cannon b.a.l.l.s were thrown in with great violence (one of them going between the spokes of Ransomes' large casting), and instantly after the dome had started, the boards of the outside scaffolding which had been tossed up by the same gust dropped down into the gap which the dome had left. It is a wonder that none of the men were hurt and that the iron was not broken. The dome is quite covered and I think does not look so well as when the hooping was visible."

"Previous to 1836 I had begun to contemplate the attachment of Magnetic Observations to the Observatory, and had corresponded with Prof. Christie, Prof. Lloyd, Prof. J. D. Forbes, and Mr Gauss on the subject. On Jan. 12th 1836 I addressed a formal letter to the Admiralty, and on Jan. 18th received their answer that they had referred it to the Board of Visitors. On March 25th I received authority for the expenditure of _30_, and I believe that I then ordered Merz's 2-foot magnet. The Visitors met on Feb. 26th and after some discussion the site was chosen and the extent of ground generally defined, and on Dec. 22nd Mr Spring Rice (Lord Monteagle) as Chancellor of the Exchequer virtually effected the transfer of the ground. But no further steps were taken in 1836. A letter on a systematic course of magnetic observations in various parts of the world was addressed by Baron Alexander Humboldt to the Duke of Suss.e.x, President of the Royal Society; and was referred to Prof. Christie and me. We reported on it on June 9th 1836, strongly recommending the adoption of the scheme.

"A plan had been proposed by the Promoters of the London and Gravesend Railway (Col. Landman, Engineer) for carrying a railway at high level across the bottom of the Park. On Jan. 9th I received orders from the Admiralty to examine into its possible effect in producing vibrations in the Observatory. After much correspondence, examination of ground, &c., I fixed upon a part of the Greenwich Railway (not yet opened for traffic) near the place where the Croydon trunk line now joins it, as the place for trains to run upon, while I made observations with a telescope viewing a collimator by reflection in mercury at the distance of 500 feet. The experiments were made on Jan. 25th, and I reported on Feb. 4th. It was shewn that there would be some danger to the Observatory. On Nov. 2nd Mr James Walker, Engineer, brought a model of a railway to pa.s.s by tunnel under the lower part of the Park: apparently this scheme was not pressed.

"In addition to the routine work of the Observatory, a special set of observations were made to determine the ma.s.s of Jupiter.--Also the Solar Eclipse of May 15th was observed at Greenwich in the manner which I had introduced at Cambridge.--The Ordnance Zenith Sector, and the instruments for the St Helena Observatory were brought for examination.--Much attention was given to chronometers, and various steps were taken for their improvement.--I had some important correspondence with Mr (Sir John) Lubbock, upon the Lunar Theory generally and his proposed empirical lunar tables. This was the first germ of the great reduction of Lunar Observations which I subsequently carried out.--In October I was nominated on the Council of the Royal Society, having been admitted a Fellow on Feb. 18th 1836. I was President of the Astronomical Society during this and the preceding year (1836 and 1835).

"My connection with Groombridge's Catalogue of Stars began in 1832, and the examination, in concert with Mr Baily, of the edition printed by Mr Henry Taylor, resulted in its condemnation. In 1834 I volunteered to the Admiralty to prepare a new edition, and received their thanks and their authority for proceeding. It required a great deal of examination of details, and much time was spent on it in 1836: but it was not brought to the state of readiness for press.

"My predecessor, Mr Pond, died on Sept. 7th 1836, and was interred in Halley's tomb in Lee churchyard."

The following letter was written by Airy in support of the application for a pension to Mrs Pond, who had been left in great distress:

To HENRY WARBURTON, ESQ.

"The points upon which in my opinion Mr Pond's claims to the grat.i.tude of Astronomers are founded, are princ.i.p.ally the following. _First_ and chief, the accuracy which he introduced into all the princ.i.p.al observations. This is a thing which from its nature it is extremely difficult to estimate now, so long after the change has been made, and I can only say that so far as I can ascertain from books the change is one of very great extent: for certainty and accuracy, Astronomy is quite a different thing from what it was, and this is mainly due to Mr Pond. The most striking exemplification of this is in his laborious working out of every conceivable cause or indication of error in the Circle and the two Circles: but very great praise is also due for the new system which he introduced in working the Transit. In comparing Mr Pond's systems of observation with Dr Maskelyne's, no one can avoid being impressed with the inferiority of Dr Maskelyne's. It is very important to notice that the continental observatories which have since attracted so much attention did not at that time exist or did not exist in vigour. _Secondly_, the attention bestowed by Mr Pond on those points (chiefly of sidereal astronomy) which he regarded as fundamental: to which such ma.s.ses of observations were directed as entirely to remove the doubts from probable error of individual observations or chance circ.u.mstances which have injured many other determinations. _Thirdly_, the regularity of observation. The effect of all these has been that, since the commencement of Mr Pond's residence at Greenwich, Astronomy considered as an accurate representation of the state of the heavens in the most material points has acquired a certainty and an extent which it never had before. There is no period in the history of the science so clean. On some matters (in regard to the choice of observations) I might say that my own judgment would have differed in some degree from Mr Pond's, but one thing could have been gained only by giving up another, and upon the general accuracy no improvement could have been made. Mr Pond understood nothing of physical astronomy; but neither did anybody else, in England.

"The supposed decrease of general efficiency in the last few years is to be ascribed to the following causes:

1. Mr Pond's ill health.