Autobiography of Sir George Biddell Airy

by George Biddell Airy

CHAPTER IX.

AT GREENWICH OBSERVATORY FROM JANUARY 1ST, 1876,
TO HIS RESIGNATION OF OFFICE ON AUGUST 15TH,
1881.

1876

"At the door from the Front Court to the staircase of the Octagon Room (the original entrance to the Observatory as erected by Sir Christopher Wren), a small porch-shelter has been often desired. I proposed to fix there a fan-roof of quadrantal form, covering the upper flat stone of the external steps.—On a critical examination of the micrometer-screws of the Transit Circle it was found that the corrections, which range from -1°38" to +0°76", indicate considerable wear in the screws; and it was found that as much as one-hundreth part of an inch had been worn away from some of the threads. The old screws were consequently discarded, and new ones were made by Mr Simms.—The adjustment of the Spectroscope has occupied a great deal of attention. There was astigmatism of the prisms; and false light reflected from the base of the prisms, causing loss both of light and of definition. The latter defect was corrected by altering the angles, and then astigmatism was corrected by a cylindrical lens near the slit. The definition in both planes was then found to be perfect.—The number of small planets has now become so great, and the interest of establishing the elements of all their orbits so small,—while at the same time the light of all those lately discovered is very faint, and the difficulty and doubt of observation greatly increased,—that I have begun to think seriously of limiting future observations to a small number of these objects.—All observations with the Spectroscope have been completely reduced; the measures of lines in the spectra of elements being converted into corresponding wave-lengths, and the observations of displacement of lines in the spectra of stars being reduced so as to exhibit the concluded motion in miles per second, after applying a correction for the earth's motion. Sixteen measures of the F line in the spectrum of the Moon as compared with hydrogen give a displacement corresponding to a motion of less than two miles a second, which seems to shew that the method of comparison now adopted is free from systematic error; and this is supported by the manner in which motions of approach and recession are distributed among the stars examined on each night of observation. The results recently obtained appear to be on the whole as consistent as can be expected in such delicate observations, and they support in a remarkable manner the conclusions of Dr Huggins, with regard to the motions of those stars which he examined.—Photographs of the sun have been taken with the photoheliograph on 182 days. On one of the photographs, which was accidentally exposed while the drop slit was being drawn up, there appears to be a faint image of a cloud-like prominence close to the sun's limb, though the exposure probably only amounted to a fraction of a second. A prominence of unusual brilliancy was seen with the Spectroscope about the same time and in the same position with reference to the Sun's limb. All groups of Sun-spots and faculae have been numbered, and the dates of their first and last appearances entered up to the present time. Areas of spots have been measured, and the measures have been reduced to millionths of the Sun's visible hemisphere.—The examination of the readings of the deep-sunk thermometers from 1846 to 1873 has exhibited some laws which had been sufficiently established before this time, and some which were less known. Among the former were the successive retardations of seasons in successive descents, amounting to about four months at the depth of 25 feet; and the successive diminutions of the annual range of temperature. Among the latter is the character of the changes from year to year, which the great length of this series of observations brings well to light. It is found that from year to year the mean temperature of the surface for the year, varying by three or four degrees of Fahrenheit, follows in its changes the mean temperature of the atmosphere for the year, and that the changes of annual temperature are propagated downwards, retarded in phase and diminishing in amount of change, in the same manner (though probably not following the same law) as the season changes. The inference from this is, that changes of temperature come entirely from the exterior and in no discoverable degree from the interior; an inference which may be important in regard both to solar action and to geology. —Referring to the Transit of Venus observations: In the astronomical part of the reductions, there has been great labour and difficulty in the determination of local sidereal times; some books of observations required extensive transcription; some instrumental errors are still uncertain; the latter determinations have perplexed us so much that we are inclined to believe that, in spite of the great facilities of reduction given by the transit instrument, it would be better to rely on the altazimuth for time-determinations…. In the photographic part, I have confined my attention entirely to measures of the distance between the centres of the Sun and Planet, a troublesome and complex operation.—Referring to the progress of the Numerical Lunar Theory: With a repetition of grant from the Treasury, I have usually maintained four junior computers on this work. The progress, though considerable, has not been so great as I had hoped, by reason of the excessive personal pressure upon me during the whole year.—I wrote a letter of congratulation to Le Verrier on the completion of his great work of Planetary Tables.—On May 13th the Queen was at South Kensington, and I attended to explain the astronomical instruments, and shewed Her Majesty one of the Transit of Venus photographs."

Of private history: He returned from his Playford visit on the 18th of January.—In April there was a two-day trip to Colchester.—From June 13th to July 12th he was travelling in the North of Scotland and the Orkneys with his daughters, staying for a short time with Mr Webster, M.P., at Aberdeen, and with Mr Newall at Newcastle.—In September there was a week's run to Birkenhead and Keswick.—In November a week's run to Playford.—From the 13th to 15th of December he was at Cambridge, and on the 28th he went to Playford for the usual winter stay there.

1877

"In April of this year I was much engaged on the subject of Mr Gill's expedition to Ascension to observe for the determination of the parallax of Mars at the approaching opposition of that planet.—A large Direct-vision Spectroscope has been quite recently made by Mr Hilger under Mr Christie's direction on a new plan, in which either great dispersion or great purity of spectrum is obtained by the use of 'Half-prisms,' according as the incident pencil falls first on the perpendicular or on the oblique face. In this Spectroscope either one or two half prisms can be used at pleasure, according to the dispersion required, and there is facility for increasing the train to three or four half-prisms, though the dispersion with two only is nearly double of that given by the large ten-prism Spectroscope. The definition in this form of Spectroscope appears to be very fine.—At the end of May 1876, spectroscopic determinations of the Sun's rotation were made by observations of the relative displacement of the Fraunhofer lines at the east and west limbs respectively. The results are in close agreement with the value of the rotation found from observations of Sun-spots. A similar determination has also been made in the case of Jupiter, with equally satisfactory results.—An Electrometer on Sir William Thomson's plan, for continuous photographic registration of atmospheric electricity has been received from Mr White of Glasgow. It was mounted in December.—The computation of the photographic records of the barometer from 1854 to 1873 has so far advanced that we can assert positively that there is no trace of lunar tide in the atmosphere; but that there is a strongly marked semi-diurnal solar tide, accompanied with a smaller diurnal tide. We are at present engaged in comparing the barometric measures with the directions of the wind.—Regarding the distribution of the printed observations: There is no extensive wish for separate magnetic observations, but general magnetic results are in great demand, especially for mining operations, and to meet this a map of magnetic declination is furnished in the newspaper called the 'Colliery Guardian.'—As regards the operations for the Transit of Venus: The computing staff has by degrees been reduced to two junior computers within the Observatory; and one or two computers external to the Observatory, who are employed on large groups of systematic calculations. The principal part of the calculations remaining at the date of the last Report was that applying to the determination of the geographical longitudes of fundamental stations. At the moment of my writing, the last of these (the longitude of Observatory Bay, Kerguelen) is not absolutely finished:… The method of determining the geographical longitude of the principal station in each group by vertical transits of the Moon has been found very successful at Honolulu and Rodriguez. For stations in high south latitude, horizontal transits are preferable.—As regards the Numerical Lunar Theory: With the view of preserving, against the ordinary chances of destruction or abandonment, a work which is already one of considerable magnitude, I have prepared and have printed as Appendix to the Greenwich Observations (with additional copies as for a separate work) the ordinary Equations of Lunar Disturbance, the novel theory of Symbolical Variations, and the Numerical Developments of the quantities on the first side of the Equations.—At various times from February to May I was engaged on the reduction of Malta Tides, and on a Paper concerning the same.—In July I was awarded the Albert Medal for my Compass corrections, and received the same from the Prince of Wales.—In February, Campbell's instrument for the registration of sunshine was introduced: it was mounted in July."

Of private history: "I was at Playford until Jan. 19th, in close correspondence as usual with Mr Christie at the Observatory, and attending to my Numerical Lunar Theory.—From Mar. 29th to Apr. 2nd I went on a short trip to Hereford, Worcester, &c.—From June 8th to 20th I was at Playford.—From Aug. 13th to Sept. 8th Airy was on an expedition in Ireland, chiefly in the North and West, with his daughters. When at Dublin he visited Grubb's instrument factory. On the return journey he stayed for some time in the Lake District of Cumberland, and took soundings in the neighbourhood of the place of the 'floating island' in Derwentwater."

Airy took the greatest interest in antiquarian matters, whether military or ecclesiastical, and his feelings on such matters is well illustrated by the following letter:

ROYAL OBSERVATORY, GREENWICH, S.E. 1877, February 27.

DEAR SIR,

I venture to ask if you can assist me in the following matter.

In the Parish Church of Playford, near Ipswich, Suffolk, was a splendid brass tombstone to Sir Thomas Felbrigg. By an act of folly and barbarism, almost unequalled in the history of the world, the Incumbent and Curate nearly destroyed the brass inscription surrounding the image of the Knight.

This tombstone is figured in Gough's Sepulchral Antiquities, which, I presume, is to be found in the British Museum.

And I take the liberty to ask if you would kindly look at the engraving, and give me any suggestion as to the way in which some copies of it could be made, in a fairly durable form. I am connected with the parish of Playford, and am anxious to preserve for it this memorial of a family of high rank formerly resident there.

I am, dear Sir,
Very faithfully yours,
G.B. AIRY.

T. Winter Jones, Esq.

To this request Mr Winter Jones immediately acceded, and the engraving was duly photographed, and copies were circulated with a historical notice of Sir George (not Sir Thomas) Felbrigg and a history of the Monument. Sir George Felbrigg was Esquire-at-Arms to Edward III., and Lord of the Manor of Playford: he died in 1400, and was buried in the North wall of Playford Church.

1878

The Report to the Board of Visitors has this paragraph: "I continue to remark the approaching necessity for Library extension. Without having absolutely decided on a site, I may suggest that I should wish to erect a brick building, about 50 feet by 20, consisting of two very low stories (or rather of one story with a gallery running round its walls), so low that books can be moved by hand without necessity for a ladder.—In the month of December, 1877, the azimuthal error of the Transit Circle had increased to 10". A skilful workman, instructed by Mr Simms, easily reduced the error to about 2".5 (which would leave its mean error nearly 0), the western Y being moved to the north so far as to reduce the reading of the transit micrometer, when pointed to the south, from 35r.500 to 35r.000. The level error was not sensibly affected.—The Sidereal Standard Clock preserves a rate approaching to perfection, so long as it is left without disturbance of the galvanic-contact springs (touched by its pendulum), which transmit signals at every second of time to sympathetic clocks and the chronograph. A readjustment of these springs usually disturbs the rate.—To facilitate the observations of stars, a new working catalogue has been prepared, in which are included all stars down to the third magnitude, stars down to the fifth magnitude which have not been observed in the last two catalogues, and a list of 258 stars of about the sixth magnitude of which the places are required for the United States Coast Survey. The whole number of stars in our new working list is about 2500. It may be here mentioned that an extensive series of observations was made, during the autumn, of about 70 stars, at the request of Mr Gill, for comparison with Mars, Ariadne, and Melpomene.—On Apr. 10th last, a very heavy fall of rain took place. Between Apr. 10d. 5h. and Apr. 11d. 2h., 2.824 inch. was recorded, and 75 per cent. of this, or 2.12 inch., fell in the eight hours between 13-1/2h. and 21-1/2h.; and on May 7, 1 inch of rain fell in 50 minutes, of which 1/2 inch fell in 15 minutes.—The supplementary compensation continues to be applied with success to Government chronometers which offer facilities for its introduction, and a marked improvement in the performance of chronometers returned after repair by the makers appears to have resulted from the increased attention now given to the compensation. Of the 29 competitive chronometers, 25 have the supplementary compensation."—With regard to the reduction of the observations of the Transit of Venus: After reference to the difficulties arising from the errors and the interpretation of the language used by some of the observers, the Report continues thus: "Finally a Report was made to the Government on July 5th, giving as the mean result for Mean Solar Parallax 8".76; the results from ingress and from egress, however, differing to the extent of 0".11…. After further examination and consideration, the result for parallax has been increased to 8".82 or 8".83. The results from photography have disappointed me much. The failure has arisen, perhaps sometimes from irregularity of limb, or from atmospheric distortion, but more frequently from faintness and from want of clear definition. Many photographs, which to the eye appeared good, lost all strength and sharpness when placed under the measuring microscope. A final result 8".17 was obtained from Mr Burton's measures, and 8".08 from Capt. Tupman's.—With regard to the Numerical Lunar Theory: A cursory collection of the terms relating to the Areas (in the Ecliptic) led me to suppose that there might be some error in the computations of the Annual Equation and related terms. A most jealous re-examination has however detected nothing, and has confirmed my belief in the general accuracy of the numerical computations. I dare not yet venture to assume an error in Delaunay's theory; but I remember that the Annual Equation gave great trouble to the late Sir John Lubbock, and that he more than once changed his conclusions as to its true value.—In February I was engaged on the drawings and preparations for my intended Lecture at Cockermouth on the probable condition of the interior of the Earth. The Lecture was delivered in April.—At different times in the autumn I was engaged on diagrams to illustrate the passage of rays through eye-pieces and double-image micrometers.—The miscellaneous scientific correspondence, which was always going on, was in this year unusually varied and heavy."

Of private history: He was at Playford till Jan. 26th.—In April he went to Cockermouth to deliver his Lecture above-mentioned: the journey was by Birmingham, where he stayed for two days (probably with his son Osmund, who resided there), to Tarn Bank (the residence of Isaac Fletcher, M.P.): the lecture was delivered on the 22nd: he made excursions to Thirlmere and Barrow, and to Edward I.'s Monument, and returned to Greenwich on the 27th.—From June 17th to 28th he was at Playford.—From Aug. 19th to Sept. 17th he was travelling in Scotland, visiting the Tay Bridge, the Loch Katrine Waterworks, &c., and spent the last fortnight of his trip at Portinscale, near Keswick. On Dec. 23rd he went to Playford.

1879

"The manuscripts of every kind, which are accumulated in the ordinary transactions of the Observatory, are preserved with the same care and arranged on the same system as heretofore. The total number of bound volumes exceeds 4000. Besides these there is the great mass of Transit of Venus reductions and manuscripts, which when bound may be expected to form about 200 volumes.—With regard to the numerous group of Minor Planets, the Berlin authorities have most kindly given attention to my representation, and we have now a most admirable and comprehensive Ephemeris. But the extreme faintness of the majority of these bodies places them practically beyond the reach of our meridian instrument, and the difficulty of observation is in many cases further increased by the large errors of the predicted places.—After a fine autumn, the weather in the past winter and spring has been remarkably bad. More than an entire lunation was lost with the Transit Circle, no observation of the Moon on the meridian having been possible between January 8 and March 1, a period of more than seven weeks. Neither Sun nor stars were visible for eleven days, during which period the clock-times were carried on entirely by the preceding rate of the clock. The accumulated error at the end of this time did not exceed 0s'3.—Some difficulty was at first experienced with the Thomson Electrometer, which was traced to want of insulation. This has been mastered by the use of glass supporters, which carry some sulphuric acid. The instrument is now in excellent order, and the photographic registers have been perfectly satisfactory since 1879, February, when the new insulators were applied.—From the annual curves of diurnal inequality, deduced from the Magnetic Reductions, most important inferences may be drawn, as to the connection between magnetic phenomena and sun-spots. These annual curves shew a well-marked change in close correspondence with the number of sun-spots. About the epoch of maximum of sun-spots they are large and nearly circular, having the same character as the curves for the summer months; whilst about the time of sun-spot minimum they are small and lemniscate-shaped, with a striking resemblance to the curves for the winter months. The connection between changes of terrestrial magnetism and sun-spots is shewn in a still more striking manner by a comparison which Mr Ellis has made between the monthly means of the diurnal range of declination and horizontal force, and Dr R. Wolf's 'relative numbers' for frequency of sun-spots.—The records of sunshine with Campbell's Registering Sun-dial are preserved in a form easily accessible for reference, and the results are communicated weekly to the Agricultural Gazette.—Prof. Oppolzer's results for the determination of the longitudes of Vienna and Berlin, made in 1877, have now been made public. They shew a remarkable agreement of the Chronometric determination formerly made with the Telegraphic. It may be of interest to recall the fact that a similar agreement was found between the Chronometric and Telegraphic determinations of the longitude of Valentia.—For observing the Transit of Venus of 1882, the general impression appears to be that it will be best to confine our observations to simple telescopic observations or micrometer observations at Ingress and Egress, if possible at places whose longitudes are known. For the first phenomenon (accelerated ingress) the choice of stations is not good; but for the other phenomena (retarded ingress, accelerated egress, retarded egress) there appears to be no difficulty.—With regard to the Numerical Lunar Theory: Respecting the discordance of Annual Equation, I suspend my judgment. I have now discussed the theory completely; and in going into details of secular changes, I am at this time engaged on that which is the foundation of all, namely, the change of excentricity of the Solar Orbit, and its result in producing Lunar Acceleration. An important error in the theoretical formulae for Variations of Radius Vector, Longitude, and Latitude, was discovered; some calculations depending on them are cancelled."—Referring to the magnitude of the printed volume of "Greenwich Observations," and the practicability of reducing the extent of it, the Report states thus: "The tendency of external scientific movement is to give great attention to the phenomena of the Solar disc (in which this Observatory ought undoubtedly to bear its part). And I personally am most unwilling to recede from the existing course of magnetical and meteorological observations….The general tendency of these considerations is to increase the annual expenses of the Observatory. And so it has been, almost continuously, for the last 42 years. The annual ordinary expenses are now between 2-1/2 and 3 times as great as in my first years at the Royal Observatory.—Mr Gill was appointed to the Cape Observatory, and I wrote out instructions for him in March: there was subsequently much correspondence respecting the equipment and repairs of the Cape Observatory."—In the Monthly Notices of the Royal Astronomical Society for January an article had appeared headed "Notes on the late Admiral Smyth's Cycle of Celestial Objects, Vol. II." by Mr Herbert Sadler. In this article Mr Sadler had criticized the work of Admiral Smyth in a manner which Airy regarded as imputing bad faith to Admiral Smyth. He at once took up the defence of his old friend very warmly, and proposed certain Drafts of Resolutions to the Council of the Society. These Resolutions were moved, but were amended or negatived, and Airy immediately resigned his office of Vice-President. There was considerable negociation on the subject, and discussion with Lord Lindsay, and on May 9th Airy's Resolutions were accepted by the Council.—In October Airy inspected the "Faraday" telegraph ship, then lying in the river near Messrs Siemens' works, and broke his finger by a fall on board the vessel.—In this year Airy wrote and circulated a letter to the Members of the Senate of the University of Cambridge, on the subject of the Papers set in the Smith's Prizes Examination. In this letter, as on former occasions, he objected much to the large number of questions in "purely idle algebra, arbitrary combinations of symbols, applicable to no further purpose." And in particular he singled out for comment the following question, which was one of those set, "Using the term circle as extending to the case where the radius is a pure imaginary, it is required to construct the common chord of two given circles." This drew forth as usual a rejoinder from Prof. Cayley, who wrote enclosing a solution of his problem, but not at all to Airy's satisfaction, who replied as follows: "I am not so deeply plunged in the mists of impossibles as to appreciate fully your explanation in this instance, or to think that it is a good criterion for University candidates."

Of private history: On Jan. 21st he returned from Playford.—On March 22nd he attended the funeral of his sister at Little Welnetham near Bury St Edmunds: Miss Elizabeth Airy had lived with him at the Observatory from shortly after his appointment.—For about a week at the end of April he was visiting Matlock, Edensor, and Buxton.—From June 14th to July 18th he was staying at Portinscale near Keswick.—He was at Playford for two or three days in October, and went there again on Dec. 23rd for his usual winter holiday.

The following letter, relating to the life of Thomas Clarkson, was
written to Dr Merivale, Dean of Ely, after reading the account in the
"Times" of October 10th of the unveiling of a statue of Clarkson near
Ware:

ROYAL OBSERVATORY, GREENWICH,
LONDON, S.E.
1879, October 11.

DEAR SIR,

Pardon my intrusion on you, in reference to a transaction which has greatly interested me—the honour paid by you to the memory of Thomas Clarkson. With very great pleasure I have heard of this step: and I have also been much satisfied with the remarks on it in the "Times." I well remember, in Clarkson's "History of the Abolition," which I read some 60 years ago, the account of the circumstance, now commemorated by you, which determined the action of his whole subsequent life.

It is not improbable that, among those who still remember Clarkson, my acquaintance with him began at the earliest time of all. I knew him, intimately, from the beginning of 1815 to his death. The family which he represented must have occupied a very good position in society. I have heard that he sold two good estates to defray the expenses which he incurred in his personal labours for Abolition: and his brother was Governor of Sierra Leone (I know not at what time appointed). Thomas Clarkson was at St John's College; and, as I gather from circumstances which I have heard him mention, must have been a rather gay man. He kept a horse, and at one time kept two. He took Orders in the Church; and on one occasion, in the course of his Abolition struggle, he preached in a church. But he afterwards resolutely laid aside all pretensions to the title of Minister of the Church, and never would accept any title except as layman. He was, however, a very earnest reader of theology during my acquaintance with him, and appeared to be well acquainted with the Early Fathers.

The precise words in which was announced the subject for Prize Essay in the University were "Anne liceat invitos in servitutem trahere."

After the first great victory on the slave trade question, he established himself in a house on the bank of Ullswater. I have not identified the place: from a view which he once shewed me I supposed it to be near the bottom of the lake: but from an account of the storm of wind which he encountered when walking with a lady over a pass, it seemed to be in or near Patterdale. When the remains of a mountaineer, who perished in Helvellyn (as described in Scott's well-known poem), were discovered by a shepherd, it was to Mr Clarkson that the intelligence was first brought.

He then lived at Bury St Edmunds. Mrs Clarkson was a lady of Bury. But I cannot assign conjecturally any dates to his removals or his marriage. His only son took his B.A. degree, I think, about 1817.

I think it was in 1814 that he began his occupation of Playford Hall—a moated mansion near Ipswich, formerly of great importance —where he lived as Gentleman Farmer, managing a farm leased from the Marquis of Bristol, and occupying a good position among the gentry of the county. A relative of mine, with whom I was most intimately acquainted, lived in the same parish (where in defiance of school rules I spent nearly half my time, to my great advantage as I believe, and where I still retain a cottage for occasional residence), and I enjoyed much of Mr Clarkson's notice. It was by his strong advice that I was sent to Cambridge, and that Trinity College was selected: he rode with me to Rev. Mr Rogers of Sproughton for introductory examination; he introduced me to Rev. C. Musgrave (subsequently of Halifax), accidentally doing duty at Grundisburgh, who then introduced me to Sedgwick, Peacock, and T. Musgrave (subsequently of York). In 1825, when I spent the summer at Keswick, he introduced me to Southey and Wordsworth.

Mr Clarkson lived about thirty years at Playford Hall, and died there, and lies interred with his wife, son, and grandson, in Playford churchyard. I joined several friends in erecting a granite obelisk to his memory in the same churchyard. His family is extinct: but a daughter of his brother is living, first married to T. Clarkson's son, and now Mrs Dickinson, of the Rectory, Wolferton.

I am, my dear Sir,
Very faithfully yours,
G.B. AIRY.

The Very Reverend,
The Dean of Ely.

1880

"The Admiralty, on final consideration of the estimates, decided not to proceed with the erection of a new Library near the Magnetic Observatory in the present year. In the mean time the space has been cleared for the erection of a building 50 by 20 feet.—I have removed the Electrometer Mast (a source of some expense and some danger), the perfect success of Sir William Thomson's Electrometer rendering all further apparatus for the same purpose unnecessary.—Many years ago a double-image micrometer, in which the images were formed by the double refraction of a sphere of quartz, was prepared by Mr Dollond for Capt. Smyth, R.N. Adopting the same principle on a larger scale, I have had constructed by Mr Hilger a micrometer with double refraction of a sphere of Iceland spar. Marks have been prepared for examination of the scale, but I have not yet had opportunity of trying it.—The spectroscopic determination of Star-motions has been steadily pursued. The stars are taken from a working list of 150 stars, which may eventually be extended to include all stars down to the fourth magnitude, and it is expected that in the course of time the motions of about 300 stars may be spectroscopically determined.—A new pressure-plate with springs has been applied by Mr Browning to Osler's Anemometer, and it is proposed to make such modification as will give a scale extending to 50 lbs. pressure on the square foot. Other parts of the instrument have also been renewed.—As regards the reduction of the magnetical results since 1863: In the study of the forms of the individual curves; their relations to the hour, the month, the year; their connection with solar or meteorological facts; the conjectural physico-mechanical causes by which they are produced; there is much to occupy the mind. I regret that, though in contemplation of these curves I have remarked some singular (but imperfect) laws, I have not been able to pursue them.—The mean temperature of the year 1879 was 46.1°, being 3.3° below the average of the preceding 38 years. The highest temperature was 80.6° on July 30, and the lowest 13.7° on Dec. 7. The mean temperature was below the average in every month of the year; the months of greatest deviation being January and December, respectively 6.8° and 7.6° below the average; the months of April, May, July, and November were each between 4° and 5° below the average. The number of hours of bright sunshine, recorded with Campbell's Sunshine Instrument, during 1879, was only 983.—In the summer of 1879 Commander Green, U.S.N., came over to this country for the purpose of determining telegraphically the longitude of Lisbon, as part of a chain of longitudes extending from South America to Greenwich. A successful interchange of signals was made with Commander Green between Greenwich and Porthcurno on four nights, 1879, June 25 to 29. The results communicated by Commander Green shew that the longitude of Lisbon Observatory, as adopted in the Nautical Almanac, requires the large correction of +8.54".—With regard to the coming Transit of Venus in 1882: From the facility with which the requirements for geographical position are satisfied, and from the rapid and accurate communication of time now given by electric telegraph, the observation of this Transit will be comparatively easy and inexpensive. I have attached greater importance than I did formerly to the elevation of the Sun…. I remark that it is highly desirable that steps be taken now for determining by telegraph the longitude of some point of Australia. I have stated as the general opinion that it will be useless to repeat photographic observations. —In April Mr Barlow called, in reference to the Enquiry on the Tay Bridge Disaster. (The Bridge had been blown down on Dec. 28th, 1879.) I prepared a memorandum on the subject for the Tay Bridge Commission, and gave evidence in a Committee Room of the House of Lords on Apr. 29th." (Much of the Astronomer Royal's evidence on this occasion had reference to the opinions which he had expressed concerning the wind-pressure which might be expected on the projected Forth Bridge, in 1873.)—In May Airy was consulted by the Postmaster-General in the matter of a dispute which had arisen between the Post Office and the Telephone Companies, which latter were alleged to have infringed the monopoly of the Post Office in commercial telegraphs: Airy made a declaration on the subject.—In July Mr Bakhuyzen came to England to determine the longitude of Leyden, on which he was engaged till Sept. 9th, and carried on his observations at the Observatory.—In July Airy was much engaged in perusing the records of Mr Gill's work at the Cape of Good Hope.

Of private history: On Jan. 24th he returned from Playford.—From June 14th to July 4th he was again at Playford.—From September 21st to October 20th he was staying at Portinscale near Keswick.—On Dec. 23rd he went again to Playford for his winter holiday.

Respecting the agitation at Cambridge for granting University degrees to women, the following extract from a letter addressed to a young lady who had forwarded a Memorial on the subject for his consideration, and dated Nov. 10th, 1880, contains Airy's views on this matter.

"I have not signed the Memorial which you sent for my consideration: and I will endeavour to tell you why. I entirely approve of education of young women to a higher pitch than they do commonly reach. I think that they can successfully advance so far as to be able clearly to understand—with gratification to themselves and with advantage to those whose education they will superintend—much of the results of the highest class of science which have been obtained by men whose lives are in great measure devoted to it. But I do not think that their nature or their employments will permit of their mastering the severe steps of beginning (and indeed all through) and the complicated steps at the end. And I think it well that this their success should be well known—as it is sure to be—among their relatives, their friends, their visitors, and all in whom they are likely to take interest. Their connection with such a place as Girton College is I think sufficient to lead to this. But I desire above all that all this be done in entire subservience to what I regard as infinitely more valuable than any amount of knowledge, namely the delicacy of woman's character. And here, I think, our views totally separate. I do not imagine that the University Degree would really imply, as regards education, anything more than is known to all persons (socially concerned in the happiness of the young woman) from the less public testimonial of the able men who have the means of knowing their merits. And thus it appears to me that the admission to University Degree would simply mean a more extended publication of their names. I dread this."

1881

"The new line of underground telegraph wires has been completed by the officers of the General Post Office. The new route is down Croom's Hill in Greenwich, and the result of this change, at least as regards the earth-current wires, and probably as regards the other wires, has not been satisfactory. It was soon found that the indications of the earth-current wires were disturbed by a continual series of petty fluctuations which almost completely masked the proper features of earth currents…. If this fault cannot be removed, I should propose to return to our original system of independent wires (formerly to Croydon and Dartford).—The new Azimuth-mark (for the Altazimuth), upon the parapet of the Naval College, is found to be perfectly satisfactory as regards both steadiness and visibility. The observations of a low star for zero of azimuth have been omitted since the beginning of 1881; the mark, in combination with a high star, appearing to give all that is necessary for this purpose.—All the instruments have suffered from the congealing of the oil during the severe weather of the past winter, and very thorough cleaning of all the moving parts has been necessary.—The Solar Eclipse of 1880, Dec. 31, was well observed. The first contact was observed by four observers and the last contact by two. The computations for the observations have been exceptionally heavy, from the circumstance that the Sun was very low (86° 14' Z.D. at the last observation) and that it has therefore been necessary to compute the refraction with great accuracy, involving the calculation of the zenith distance for every observation. And besides this, eighty-six separate computations of the tabular R.A. and N.P.D. of cusps have been required.—Amongst other interesting spectroscopic observations of the Sun, a remarkable spectrum of a sun-spot shewing 17 strong black lines or bands, each as broad as b_1, in the solar spectrum, was observed on 1880, Nov. 27 and 29. These bands to which there is nothing corresponding in the Solar Spectrum (except some very faint lines) have also been subsequently remarked in the spectrum of several spots.—The Police Ship 'Royalist' (which was injured by a collision in 1879 and had been laid up in dock) has not been again moored in the river, and the series of observations of the temperature of the Thames is thus terminated. —Part of the month of January 1881 was, as regards cold, especially severe. The mean temperature of the period January 12 to 26 (15 days) was only 24.2°, or 14.7° below the average; the temperature fell below 20° on 10 days, and rose above the freezing point only on 3 days. The highest temperature in this period was 35.3°, the lowest 12.7°. On January 17th (while staying at Playford) my son Hubert and I noticed an almost imperceptible movement in the upper clouds from the South-East. On that night began the terrible easterly gale, accompanied with much snow, which lasted to the night of the 18th. The limiting pressure of 50 lbs. on the square foot of Osler's Anemometer was twice exceeded during this storm.—With respect to the Diurnal Inequalities of Magnetic Horizontal Force: Assuming it to be certain that they originate from the Sun's power, not immediately, but mediately through his action on the Earth, it appears to me (as I suggested long ago) that they are the effects of the attraction of the red end or north end of the needle by the heated portions of our globe, especially by the heated sea, whose effect appears to predominate greatly over that of the land. I do not say that everything is thus made perfectly clear, but I think that the leading phenomena may be thus explained. And this is almost necessarily the way of beginning a science.—In the first few years after the strict and systematic examination of competitive chronometers, beginning with 1856, the accuracy of chronometers was greatly increased. For many years past it has been nearly stationary. I interpret this as shewing that the effects of bad workmanship are almost eliminated, and that future improvement must be sought in change of some points of construction.—Referring to the Transit of Venus in 1874, the printing of all sections of the Observations, with specimens of the printed forms employed, and remarks on the photographic operations, is very nearly completed. An Introduction is begun in manuscript. I am in correspondence with the Commission which is entrusted with the arrangements for observation of the Transit of 1882.—The Numerical Lunar Theory has been much interrupted by the pressure of the Transit of Venus work and other business."—In his Report to the Board of Visitors (his 46th and last), Airy remarks that it would be a fitting opportunity for the expression of his views on the general objects of the Observatory, and on the duties which they impose on all who are actively concerned in its conduct. And this he proceeds to do in very considerable detail.—On May 5th he wrote to Lord Northbrook (First Lord of the Admiralty) and to Mr Gladstone to resign his post of Astronomer Royal. From time to time he was engaged on the subject of a house for his future residence, and finally took a lease of the White House at the top of Croom's Hill, just outside one of the gates of Greenwich Park. On the 15th of August he formally resigned his office to Mr W.H.M. Christie, who had been appointed to succeed him as Astronomer Royal, and removed to the White House on the next day, August 16th.

His holiday movements in the portion of the year up to August 16th consisted in his winter visit to Playford, from which he returned on Jan. 24th: and a subsequent visit to Playford from June 7th to 18th.

* * * * *

The following correspondence relating to Airy's retirement from office testifies in a remarkable manner to the estimation in which his services were held, and to the good feeling which subsisted between him and his official superiors.

10, DOWNING STREET, WHITEHALL, June 6, 1881.

DEAR SIR GEORGE AIRY,

I cannot receive the announcement of your resignation, which you have just conveyed to me, without expressing my strong sense of the distinction you have conferred upon the office of Astronomer Royal, and of the difficulty of supplying your place with a person of equal eminence. Let me add the expression of my best wishes for the full enjoyment of your retirement from responsibility.

I remain, dear Sir George Airy,
Faithfully yours,
W.E. GLADSTONE.

* * * * *

ADMIRALTY, June 10th, 1881.

SIR,

I am commanded by my Lords Commissioners of the Admiralty to acknowledge the receipt of your letter of the 4th instant, intimating your desire to retire on the 15th August next from the office of Astronomer Royal.

2. In reply I am to acquaint you that your wishes in this matter have been communicated to the Prime Minister, and that the further necessary official intimation will in due course be made to the Treasury.

3. At the same time I am instructed by their Lordships to convey to you the expression of their high appreciation of the remarkably able and gifted manner, combined with unwearied diligence and devotion to the Public Service (especially as regards the Department of the State over which they preside), in which you have performed the duties of Astronomer Royal throughout the long period of forty-five years.

4. I am further to add that their Lordships cannot allow the present opportunity to pass without giving expression to their sense of the loss which the Public Service must sustain by your retirement, and to the hope that you may long enjoy the rest to which you are so justly entitled.

I am, Sir,
Your obedient Servant,
ROBERT HALL.

Sir G. B. Airy, K.C.B.
&c., &c.,
Royal Observatory, Greenwich.

* * * * *

ADMIRALTY, 28th June, 1881.

SIR,

My Lords Commissioners of the Admiralty have much pleasure in transmitting copy of a resolution passed by the Board of Visitors of the Royal Observatory on the 4th June last, bearing testimony to the valuable services you have rendered to Astronomy, to Navigation, and the allied Sciences throughout the long period during which you have presided over the Royal Observatory.

I am, Sir,
Your obedient Servant,
ROBERT HALL.

Sir George Biddell Airy, K.C.B.
&c., &c., &c.,
Royal Observatory, Greenwich.

"The Astronomer Royal (Sir George B. Airy) having announced his intention of shortly retiring from his position at the Royal Observatory, the following resolution proposed by Professor J. C. Adams, and seconded by Professor G. G. Stokes, was then unanimously adopted and ordered to be recorded in the Minutes of the Proceedings.

"The Board having heard from the Astronomer Royal that he proposes to terminate his connection with the Observatory on the 15th of August next, desire to record in the most emphatic manner their sense of the eminent services which he has rendered to Astronomy, to Navigation and the allied Sciences, throughout the long period of 45 years during which he has presided over the Royal Observatory.

"They consider that during that time he has not only maintained but has greatly extended the ancient reputation of the Institution, and they believe that the Astronomical and other work which has been carried on in it under his direction will form an enduring monument of his Scientific insight and his powers of organization.

"Among his many services to Science, the following are a few which they desire especially to commemorate:

(a) "The complete re-organization of the Equipment of the Observatory.

(b) "The designing of instruments of exceptional stability and delicacy suitable for the increased accuracy of observation demanded by the advance of Astronomy.

(c) "The extension of the means of making observations of the Moon in such portions of her orbit as are not accessible to the Transit Circle.

(d) "The investigation of the effect of the iron of ships upon compasses and the correction of the errors thence arising.

(e) "The Establishment at the Observatory and elsewhere of a System of Time Signals since extensively developed by the Government.

"The Board feel it their duty to add that Sir George Airy has at all times devoted himself in the most unsparing manner to the business of the Observatory, and has watched over its interests with an assiduity inspired by the strongest personal attachment to the Institution. He has availed himself zealously of every scientific discovery and invention which was in his judgment capable of adaptation to the work of the Observatory; and the long series of his annual reports to the Board of Visitors furnish abundant evidence, if such were needed, of the soundness of his judgment in the appreciation of suggested changes, and of his readiness to introduce improvements when the proper time arrived. While maintaining the most remarkable punctuality in the reduction and publication of the observations made under his own superintendance, he had reduced, collected, and thus rendered available for use by astronomers, the Lunar and Planetary Observations of his predecessors. Nor can it be forgotten that, notwithstanding his absorbing occupations, his advice and assistance have always been at the disposal of Astronomers for any work of importance.

"To refer in detail to his labours in departments of Science not directly connected with the Royal Observatory may seem to lie beyond the province of the Board. But it cannot be improper to state that its members are not unacquainted with the high estimation in which his contributions to the Theory of Tides, to the undulatory theory of Light, and to various abstract branches of Mathematics are held by men of Science throughout the world.

"In conclusion the Board would express their earnest hope, that in his retirement Sir George Airy may enjoy health and strength and that leisure for which he has often expressed a desire to enable him not only to complete the numerical Lunar Theory on which he has been engaged for some years past, but also to advance Astronomical Science in other directions."

* * * * *

ADMIRALTY, 27th October, 1881.

SIR,

I am commanded by my Lords Commissioners of the Admiralty to transmit to you, herewith, a copy of a Treasury Minute, awarding you a Special Pension of £1100 a year, in consideration of your long and brilliant services as Astronomer Royal.

I am, Sir,
Your obedient Servant,
ROBERT HALL.

Sir G.B. Airy, K.C.B., F.R.S., &c., &c.
The White House, Croom's Hill, Greenwich.

Copy of Treasury Minute, dated 10th October, 1881:

My Lords have before them a statement of the services of Sir George
Biddell Airy, K.C.B., F.R.S., who has resigned the appointment of
Astronomer Royal on the ground of age.

Sir George Airy has held his office since the year 1835, and has also, during that period, undertaken various laborious works, demanding scientific qualifications of the highest order, and not always such as could strictly be said to be included among the duties of his office.

The salary of Sir G. Airy as Astronomer Royal is £1200 a year, in addition to which he enjoys an official residence rent free, and, under ordinary circumstances he would be entitled to a pension equal to two-thirds of his salary and emoluments.

My Lords, however, in order to mark their strong sense of the distinction which, during a long and brilliant career Sir George Airy has conferred upon his office, and of the great services which, in connection with, as well as in the discharge of, his duties, he has rendered to the Crown and the Public, decide to deal with his case under the IXth Section of the Superannuation Act, 1859, which empowers them to grant a special pension for special services.

Accordingly my Lords are pleased to award to Sir George Biddell Airy,
K.C.B., F.R.S., a special Retired Allowance of £1100 per annum.

* * * * *

THE WHITE HOUSE,
CROOM'S HILL, GREENWICH,
1881, October 29.

SIR,

I have the honour to acknowledge your letter of October 27, transmitting to me, by instruction of The Lords Commissioners of Admiralty, copy of a Treasury Minute dated 1881 October 10, in which the Lords Commissioners of Her Majesty's Treasury are pleased to award to me an annual retired allowance of £1100 per annum.

Acknowledging the very liberal award of the Lords Commissioners of Treasury, and the honourable and acceptable terms in which it is announced, I take leave at the same time to offer to Their Lordships of the Admiralty my recognition of Their Lordships' kindness and courtesy in thus handing to me copy of the Treasury Minute.

I have the honour to be, Sir,
Your very obedient Servant,
G.B. AIRY.

The Secretary of the Admiralty,

* * * * *

From the Assistants of the Royal Observatory, with whom he was in daily communication, whose faithful and laborious services he had so often thankfully recognized in his Annual Reports to the Board of Visitors, and to whom so much of the credit and success of the Observatory was due, he received the following address:

ROYAL OBSERVATORY, GREENWICH, 1881, August 11.

DEAR SIR,

We cannot allow the official relation which has so long existed between yourself and us to terminate without expressing to you our sense of the admirable manner in which you have, in our opinion, upheld the dignity of the office of Astronomer Royal during the many years that you have occupied that important post.

Your long continued and varied scientific work has received such universal recognition from astronomers in all lands, that it is unnecessary for us to do more than assure you how heartily we join in their appreciation of your labours. We may however add that our position has given us opportunities of seeing that which others cannot equally well know, the untiring energy and great industry which have been therein displayed throughout a long and laborious career, an energy which leads you in retirement, and at fourscore years of age, to contemplate further scientific work.

We would ask you to carry with you into private life the best wishes of each one of us for your future happiness, and that of your family, expressing the hope that the days of retirement may not be few, and assuring you that your name will long live in our remembrance.

We are, dear Sir,
Yours very faithfully,
W.H.M. CHRISTIE, EDWIN DUNKIN, WILLIAM
ELLIS, GEORGE STRICKLAND CRISWICK, W.
C. NASH, A.M.W. DOWNING, EDWARD W.
MAUNDER, W.G. THACKERAY, THOMAS LEWIS.

Sir G.B. Airy, K.C.B., &c., &c.,
Astronomer Royal.

* * * * *

ROYAL OBSERVATORY, GREENWICH,
1881, August 13.

MY DEAR MR CHRISTIE,
and Gentlemen of the Royal Observatory,

With very great pleasure I have received your letter of August 11. I thank you much for your recognition of the general success of the Observatory, and of a portion of its conduct which—as you remark—can scarcely be known except to those who are every day engaged in it: but I thank you still more for the kind tone of your letter, which seems to shew that the terms on which we have met are such as leaves, after so many years' intercourse, no shadow of complaint on any side.

Reciprocating your wishes for a happy life, and in your case a progressive and successful one,

I am,
My dear Mr Christie and Gentlemen,
Yours faithfully,
G.B. AIRY.

* * * * *

Throughout his tenure of office Airy had cultivated and maintained the most friendly relations with foreign astronomers, to the great advantage of the Observatory. Probably all of them, at one time or another, had visited Greenwich, and to most of them he was well known. On his retirement from office he received an illuminated Address from his old friend Otto Struve and the staff of the Pulkowa Observatory, an illuminated Address from the Vorstand of the Astronomische Gesellschaft at Berlin signed by Dr Auwers and the Secretaries, a complimentary letter from the Academy of Sciences at Amsterdam, and friendly letters of sympathy from Dr Gould, Prof. Newcombe, Dr Listing, and from many other scientific friends and societies. His replies to the Russian and German Addresses were as follows:

ROYAL OBSERVATORY, GREENWICH, 1881, August 5.

MY DEAR SIR,

I received, with feelings which I will not attempt to describe, the Address of yourself and the Astronomers of Pulkowa generally, on the occasion of my retirement from the office of Astronomer Royal. I can scarcely credit myself with possessing all the varied claims to your scientific regard which you detail. I must be permitted to attribute many of them to the long and warm friendship which has subsisted so long between the Directors of the Pulkowa Observatory and myself, and which has influenced the feelings of the whole body of Astronomers attached to that Institution. On one point, however, I willingly accept your favourable expressions—I have not been sparing of my personal labour—and to this I must attribute partial success on some of the subjects to which you allude.

In glancing over the marginal list of scientific pursuits, I remark with pleasure the reference to Optics. I still recur with delight to the Undulatory Theory, once the branch of science on which I was best known to the world, and which by calculations, writings, and lectures, I supported against the Laplacian School. But the close of your remarks touches me much more—the association of the name of W. Struve and my own. I respected deeply the whole character of your Father, and I believe that he had confidence in me. From our first meeting in 1830 (on a Commission for improvement of the Nautical Almanac) I never ceased to regard him as superior to others. I may be permitted to add that the delivery of his authority to the hands of his son has not weakened the connection of myself with the Observatory of Poulkova.

Acknowledging gratefully your kindness, and that of all the Astronomers of the Observatory of Poulkova, and requesting you to convey to them this expression,

I am, my dear Sir,
Yours most truly,
G.B. AIRY.

To M. Otto von Struve,
Director of the Observatory of Poulkova
and the Astronomers of that Observatory.

* * * * *

ROYAL OBSERVATORY, GREENWICH, 1881, August 3.

MY DEAR SIR,

With very great pleasure I received the Address of the Astronomische Gesellschaft on occasion of my intended resignation of the Office of Astronomer Royal: dated July 27, and signed by yourself as President and Messrs Schoenfeld and Winnecke as Secretaries of the Astronomische Gesellschaft. I thank you much for the delicacy of your arrangement for the transmission of this document by the hands of our friend Dr Huggins. And I think you will be gratified to learn that it arrived at a moment when I was surrounded by my whole family assembled at my jour-de-fête, and that it added greatly to the happiness of the party.

I may perhaps permit myself to accept your kind recognition of my devotion of time and thought to the interests of my Science and my Office. It is full reward to me that they are so recognized. As to the success or utility of these efforts, without presuming, myself, to form an opinion, I acknowledge that the connection made by the Astronomische Gesellschaft, between my name and the advance of modern astronomy, is most flattering, and will always be remembered by me with pride.

It is true, as is suggested in your Address, that one motive for my resignation of Office was the desire to find myself more free for the prosecution of further astronomical investigations. Should my health remain unbroken, I hope to enter shortly upon this undertaking.

Again acknowledging the kindness of yourself and the Vorstand of the Astronomische Gesellschaft, and offering my best wishes for the continued success of that honourable institution,

I am, my dear Sir,
Yours very truly,
G.B. AIRY.

To Dr Aimers and the Vorstand of the Astronomische Gesellschaft.