The Royal Observatory, Greenwich: A Glance at Its History and Work

Halley's work is represented at the Observatory by two of his instruments which are still preserved there, and which hang on the west wall of the present transit room: the Iron Quadrant afterwards made famous by the observations of Bradley, and 'Halley's Transit,' the first of the great series of instruments upon which the fame of Greenwich chiefly rests. This transit instrument seems to have been set up in a small room at the west end of what is now known as the North Terrace. His quadrant was mounted on the pier which is now the base of the pier of the astrographic telescope. This pier was the first extension which the Observatory received from the original building.

On the breakdown of his health Halley nominated as his successor, James Bradley; indeed, it is stated that he offered to resign in his favour. He had known him then for over twenty years, and that keen and generous appreciation of merit in others which was characteristic of Halley had led him very early to recognize Bradley's singular ability.

James Bradley was born in 1692 or 1693, of an old North of England family. His birthplace was Sherbourne, in Gloucestershire, and he was educated at North Leach Grammar School and at Baliol College, Oxford. During the years of his undergraduateship he resided much with his uncle, the Rev. James Pound, Rector of Wanstead, Essex, an ardent amateur astronomer, a frequent visitor at the Observatory in Flamsteed's time, and one of the most accurate observers in the country. From him, no doubt, he derived his love of the science, and possibly some of his skill in observation.

Bradley's earliest observations seem to have been devoted to the phenomena of Jupiter's satellites and to the measures of double stars. The accuracy with which he followed up the first drew the attention of Halley, and so began a friendship which lasted through life. His observations of double stars, particularly of Castor, only just failed to show him the orbital movement of the pair, because his attention was drawn to other subjects before it had become sufficiently obvious.

In 1719 Bradley and his uncle made an attempt to determine the distance of the sun through observations of Mars when in opposition, observations which were so accurate that they sufficed to show that the distance of the sun could not be greater than 125 millions of miles, nor less than about 94 millions. The lower limit which they thus found has proved to be almost exactly correct, our best modern determinations giving it as 93 millions. The instrument with which the observations were made was a novel one, being 'moved by a machine that made it to keep pace with the stars;' in other words, it was the first, or nearly the first, example of what we should now call a clock-driven equatorial.

That same year he was offered the Vicarage of Bridstow, near Ross, in Monmouthshire, where, having by that time taken priest's orders, he was duly installed, July, 1720. To this was added the sinecure Rectory of Llandewi-Velgry; but he held both livings only a very short time. In 1721 the death of Dr. John Keill rendered vacant the Savilian Professorship of Astronomy at Oxford, for which Bradley became a candidate, and was duly elected, and resigned his livings in consequence.

It was whilst he was Savilian Professor that Bradley made that great discovery which will always be associated with his name. Though professor at Oxford, he had continued to assist his uncle, Mr. Pound, at his observations at Wanstead, and after the death of the latter he still lived there as much as possible, and continued his astronomical work. But in 1725 he was invited by Mr. Samuel Molyneux, who had set up a twenty-four-foot telescope made by Graham as a zenith tube at his house on Kew Green, to verify some observations which he was making. These were of the star Gamma Draconis, a star which passes through the zenith of London, and which, therefore, had been much observed both by Flamsteed and Hooke, inasmuch as by fixing a telescope in an absolutely vertical position—a position which could be easily verified—it was easy to ascertain if there was any minute change in the apparent position of the star. Dr. Hooke had declared that there was such a change, a change due to the motion of the earth in its orbit, which would prove that the star was not an infinite distance from the earth, the seeming change of its place in the sky corresponding to the change in the place of the earth from which the observer was viewing it.

Bradley found at once that there was such a change—a marked one. It amounted to as much as 1´´ of arc in three days; but it was not in the direction in which the parallax of the star would have moved it, but in the opposite. Whether, therefore, the star was near enough to show any parallax or not, some other cause was giving rise to an apparent displacement of the star, which entirely masked and overcame the effect of parallax.

So far, Bradley had but come to the same point which Flamsteed had reached. Flamsteed had detected precisely the same apparent displacement of stars, and, like Hooke, had ascribed it to parallax. Cassini had shown that this could not be the case, as the displacement was in the wrong direction; and there the matter had rested. Bradley now set to follow the question up. Other stars beside Gamma Draconis were found to show a displacement of the same general character, but the amount varied with their distance from the plane of the ecliptic, the earth's orbit. The first explanation suggested was that the axis of the earth, which moves very nearly parallel to itself as the earth moves round the sun, underwent a slight regular 'wobble' in the course of a year. To check this, a star was observed on the opposite side of the pole from Gamma Draconis; then Bradley investigated as to whether refraction might explain the difficulty, but again without success. He now was most keenly interested in the problem, and he purchased a zenith telescope of his own, made, like that of Molyneux, by Graham, and mounted it in his aunt's house at Wanstead, and observed continuously with it. The solution of the problem came at last to him as he was boating on the Thames. Watching a vane at the top of the mast, he saw with surprise that it shifted its direction every time that the boat was put about. Remarking to the boatmen that it was very odd that the wind should change just at the same moment that there was a shift in the boat's course, they replied that there was no change in the wind at all, and that the apparent change of the vane was simply due to the change of direction of the motion of the boat.

This was the celebrated discovery of the Aberration of Light, a triumph of exact observation and of clear insight. As to the exactness of Bradley's observations, it is sufficient to say that his determination of the value of the 'Constant of Aberration' gave it as 20·39´´; the value adopted to-day is 20·47´´.

On the death of Halley, in 1742, Bradley was appointed to succeed him. He found the Observatory in as utterly disheartening a condition as his predecessors had done. As already mentioned, Halley had not the same qualifications as an observer that Flamsteed had. He was, further, an old man when appointed to the post, he had no assistant provided for him, and the last five years of his life his health and strength had entirely given way. Under these circumstances, it was no wonder that Bradley found the instruments of the Observatory in a deplorable state. Nevertheless, he set to work most energetically, and in the year of his appointment he made 1500 observations in the last five months of the year. He was particularly earnest in examining the condition and the errors of his instruments; and as their defects became known to him, he was more and more anxious for a better equipment. He moved the Royal Society, therefore, to apply on his behalf for the instruments he required; and a petition from that body, in 1748, obtained what in those days must be considered the generous grant of £1000, the proceeds of the sale of old Admiralty stores. The principal instruments purchased therewith were a mural quadrant and a transit instrument, both eight feet in focal length, still preserved on the walls of the transit-room. It is interesting also to note that, following in the steps of Halley, and forecasting, as it were, the magnetic observatory which Airy would found, he devoted £20 of the grant to purchasing magnetic instruments.

Meantime he had continued his observations on aberration, and had discovered that the aberration theory was not sufficient entirely to account for the apparent changes in places of stars which he had discovered. A second cause was at work, a movement of the earth's axis, a 'wobble' in its inclination, technically known as Nutation, which is due to the action of the moon, and goes through its course in a period of nineteen years.

Beside these two great discoveries of aberration and nutation, Bradley's reputation rests upon his magnificent observations of the places of more than three thousand stars. This part of his work was done with such thoroughness, that the star-places deduced from them form the basis of most of our knowledge as to the actual movements of individual stars. In particular, he was careful to investigate and to correct for the errors of his instrument, and to determine the laws of refraction, introducing corrections for changes in the readings of thermometer and barometer. His tables of refraction were used, indeed, for seventy years after his death. Of his other labours it may be sufficient to refer to his determination of the longitudes of Lisbon and of New York, and to his effort to ascertain the parallax of the sun and moon, in combination with La Caille, who was observing at the Cape of Good Hope.

As Astronomer Royal, Bradley's great achievement was the high standard to which he raised the practical work of observation. From his day onwards, also, there was always at least one assistant. His first assistant was his own nephew, John Bradley, who received the munificent salary of ten shillings a week. Still, this was not out of proportion to the then salary of the Astronomer Royal, which practically amounted only to £90. However, in 1752, Bradley was awarded a Crown pension of £250 a year. He refused the living of Greenwich, which was offered him in order to increase his emoluments, on the ground that he could not suitably fulfil the double office. Bradley's later assistants were Charles Mason and Charles Green.

Bradley's last work was the preparation for the observations of the transit of Venus of 1761, according to the lines laid down by his predecessor, Halley. His health gave way, and he became subject to melancholia, so that the actual observations were taken by the Rev. Nathaniel Bliss, who succeeded him in his office after his death, in 1762. He was buried at Minchinhampton.

So far as we know Bradley's character, he seems to have been a gentle, modest, unassuming man, entirely free from self-seeking, and indifferent to personal gain. He was in many ways an ideal astronomer, exact, methodical, and conscientious to the last degree. His skill as an observer was his chief characteristic; and though his abilities were not equal as a mathematician or a mechanician, yet, on the one hand, he had a very clear insight into the meaning of his observations, and, on the other, he was skilful enough to himself adjust, repair, and improve his instruments.

Of Bradley's instruments, there are still preserved his famous twelve-and-a-half-foot zenith sector, with which he made his two great discoveries; his brass quadrant, which in 1750 he substituted for Halley's iron quadrant; his transit instrument, and equatorial sector. Bradley added to the buildings of the Observatory that portion which is now represented by the upper and lower computing rooms, and the chronometer room, which adjoins the latter. This room—the chronometer room—was his transit room, and the position of the shutters is still marked by the window in the roof.

The Rev. Nathaniel Bliss, who succeeded Bradley, only held the office for a couple of years, and during that time was much at Oxford. He, therefore, has left no special mark behind him as Astronomer Royal.

He was born November 28, 1700. His father, like himself, Nathaniel Bliss, was a gentleman, of Bisley, Gloucestershire.

Bliss graduated at Pembroke College, Oxford, as B.A. in 1720, and M.A. in 1723. He became the Rector of St. Ebb's, Oxford, in 1736, and on Halley's death succeeded him as Savilian Professor of Geometry. He supplied Bradley with his observations of Jupiter's satellites, and from time to time, at his request, rendered him some assistance at the Royal Observatory. This was particularly the case, as has been already mentioned, with respect to the transit of Venus of 1761, the observations of which were carried out by Bliss, owing to Bradley's ill-health. It was natural, therefore, that on Bradley's death he should succeed to the vacant post; but he held it too short a time to do any distinctive work. Such observations as he made seem to have been entirely in continuation of Bradley's. He took a great interest, however, in the improvement of clocks, a department in which so much was being done at this time by Graham, Ellicott, and others.

Nevil Maskelyne, the fifth Astronomer Royal, was, like Bliss, a close friend of Bradley's. He was the third son of a wealthy country gentleman, Edmund Maskelyne, of Purton, in Wiltshire. Maskelyne was born in London, October 6, 1732, and was educated at Westminster School. Thence he proceeded to Cambridge, where he graduated seventh Wrangler in 1754. He was ordained to the curacy of Barnet in 1755, and, twenty years later, was presented by his nephew, Lord Clive, to the living of Shrawardine, in Shropshire. In 1782 he was presented by his college to the Rectory of North Runcton, Norfolk.

The event which turned his thoughts in the direction of astronomy was the solar eclipse of July 25, 1748; and about the time that he was appointed to the curacy of Barnet he became acquainted with Bradley, then the Astronomer Royal, to whom he gave great assistance in the preparation of his table of refractions.

Like Halley before him, he made an astronomical expedition to the island of St. Helena. This was for the special purpose of observing the transit of Venus of June 6, 1761, Bradley having induced the Royal Society to send him out for that purpose. Here he stayed ten months, and made many observations. But though the transit of Venus was his special object, it was not the chief result of the expedition: not because clouds hindered his observations, but because the voyage gave him the especial bent of his life.

Halley had actually held a captain's commission in the Royal Navy, and commanded a ship; Maskelyne, more than any of the Astronomers Royal before or since, made the improvement of the practical business of navigation his chief aim. None of all the incumbents of the office kept its original charter—'To find the so much desired Longitude at Sea, for the perfecting the Art of Navigation,' so closely before him.

The solution of the problem was at hand at this time—its solution in two different ways. On the one hand, the offer by the Government of a reward of £20,000 for a clock or watch which should go so perfectly at sea, notwithstanding the tossing of the ship and the wide changes of temperature to which it might be exposed, that the navigator might at any moment learn the true Greenwich time from it, had brought out the invention of Harrison's time-keeper; on the other hand, the great improvement that had now taken place in the computation of tables of the moon's motion, and the more accurate star-catalogues now procurable, had made the method of 'lunars,' suggested a hundred and thirty years before by the Frenchman, Morin, and others, a practicable one.

There are, of course, difficulties in the way of working out this method. One is, that whilst it takes the sun but twenty-four hours to move round the sky from one noon to the next, and consequently its movements, from which the local time is inferred, are fairly rapid, the moon takes nearly twenty-eight days to move amongst the stars from the neighbourhood of one particular star round to that particular star again. Consequently, it is much easier to determine the local time with a given degree of exactness than the Greenwich time; it is something like the difference of reading a clock from both hands and from the hour hand alone.

There are other difficulties in the case which make the computation a long and laborious one, and difficult in that sense; but they do not otherwise affect its practicability.

During this voyage to St. Helena, both when outward bound and when returning, Maskelyne gave the method of 'lunars' a very thorough testing, and convinced himself that it was capable of giving the information required. For by this time the improvement of the sextant, or quadrant as it then was, by the introduction of a second mirror, by Hadley, had rendered the actual observation at sea of lunar distances, and of altitudes generally, a much more exact operation.

This conclusion he put at once to practical effect, and, in 1763, he published the British Mariner's Guide, a handbook for the determination of the longitude at sea by the method of lunars.

At the same time, the other method, that by the time-keeper or chronometer, was practically tested by him. The time-keeper constructed by John Harrison had been tested by a voyage to Jamaica in 1761, and now, in 1763, another time-keeper was tested in a voyage to Barbadoes. Charles Green, the assistant at Greenwich Observatory, was sent in charge of the chronometer, and Maskelyne went with him to test its performance, in the capacity of chaplain to his Majesty's ship Louisa.

The position which Maskelyne had already won for himself as a practical astronomer, and the intimate relations into which he had entered with Bradley and Bliss, made his appointment to the Astronomer Royalship, on the death of the latter, most suitable. At once he bent his mind to the completion of the revolution in nautical astronomy which his British Mariner's Guide had inaugurated, and in the year after his appointment he published the first number of the Nautical Almanac, together with a volume entitled, Tables Requisite to be Used with the Nautical Ephemeris, the value of which was so instantly appreciated, that 10,000 copies were sold at once.

The Nautical Almanac was Maskelyne's greatest work, and it must be remembered that he carried it on from this time up to the day of his death—truly a formidable addition to the routine labours of an Astronomer Royal who had but a single assistant on his staff. The Nautical Almanac was, however, in the main not computed at the Observatory; the calculations were effected by computers living in different parts of the country, the work being done in duplicate, on the principle which Flamsteed had inaugurated in the preparation of his Historia Cœlestis.

Maskelyne's next service to science was almost as important. He arranged that the regular and systematic publication of the observations made at Greenwich should be a distinct part of the duties of an Astronomer Royal, and he procured an arrangement by which a special fund was set apart by the Royal Society for printing them. His observations covering the years 1776 to 1811 fill four large folio volumes, and though, as already stated, he had but one assistant, they are 90,000 in number. Thus it was Maskelyne who first rendered effective the design which Charles II. had in the establishment of the Observatory. Flamsteed and Halley had been too jealous of their own observations to publish; Bradley's observations—though he himself was entirely free from this jealousy—were made, after his death, the subject of litigation by his heirs and representatives, who claimed an absolute property in them, a claim which the Government finally allowed. None of the three, however much their work ultimately tended to the improvement of the art of navigation, made that their first object. Whereas Maskelyne set this most eminently practical object in the forefront, and so gave to the Royal Observatory, which under his predecessors somewhat resembled a private observatory, its distinctive characteristics of a public institution.

It fell to Maskelyne to have to advise the Government as to the assignment of their great reward of £20,000 for the discovery of the longitude at sea. Maskelyne, while reporting favourably of the behaviour of Harrison's time-keeper, considered that the method of 'lunars' was far too important to be ignored, and he therefore recommended that half the sum should be given to Harrison for his watch, whilst the other half was awarded for the lunar tables which Mayer, before his death, had sent to the Board of Longitude. This decision, though there can be no doubt it was the right one, led to much dissatisfaction on the part of Harrison, who urged his claim for the whole grant very vigorously; and eventually the whole £20,000 was paid him. The whole question of rewards to chronometer-makers must have been one which caused Maskelyne much vexation. He was made the subject of a bitter and most voluminous attack by Thomas Mudge, for having preferred the work of Arnold and Earnshaw to his own.

Otherwise his reign at the Observatory seems to have been a singularly peaceful one, and there is little to record about it beyond the patient prosecution, year by year, of an immense amount of sober, practical work. To Maskelyne, however, we owe the practice of taking a transit of a star over five wires instead of over one, and he provided the transit instrument with a sliding eye-piece, to get over the difficulty of the displacement which might ensue if the star were observed askew when out of the centre of the field. To Maskelyne, too, we owe in a pre-eminent degree the orderly form of recording, reducing, and printing the observations. Much of the work in this direction which is generally ascribed to Airy was really due to Maskelyne. Indeed, without a wonderful gift of organization, it would have been impossible to plan and to carry the Nautical Almanac.

Beside the editing of various works intended for use in nautical astronomy or in general computation, the chief events of his long reign at Greenwich were the transit of Venus in 1769, which he himself observed, and for which he issued instructions in the Nautical Almanac; and his expedition in 1774 to Scotland, where he measured the deviation of the plumb-line from the vertical caused by the attraction of the mountain Schiehallion, deducing therefrom the mean density of the earth to be four and a half times that of water.

He died at the Observatory, February 9, 1811, aged 79, leaving but one child, a daughter, who married Mr. Anthony Mervin Story, to whom she brought the family estates in Wiltshire, inherited by Maskelyne on the deaths of his elder brothers, and, in consequence, Mr. Story added the name of Maskelyne to his own.

Maskelyne's character and policy as Astronomer Royal have been sufficiently dwelt upon. His private character was mild, amiable, and generous. 'Every astronomer, every man of learning, found in him a brother;' and, in particular, when the French Revolution drove some French astronomers to this country to find a refuge, they received from the Astronomer Royal the kindest reception and most delicate assistance.

Maskelyne added no instrument to the Observatory during his reign, though he improved Bradley's transit materially. He designed the mural circle, but it was not completed until after his death. His additions to the Observatory buildings consisted of three new rooms in the Astronomer Royal's house, and the present transit circle room.

John Pond was recommended by Maskelyne as his successor at Greenwich. At the time of his succession he was forty-four years of age, having been born in 1767. He was educated at Trinity College, Cambridge, and then spent some considerable time travelling in the south of Europe and Egypt. On his return home he settled at Westbury, where he erected an altazimuth by Troughton, with a two-and-a-half-foot circle. A born observer, his observations of the declinations of some of the principal fixed stars showed that the instrument which Maskelyne was using at Greenwich—the quadrant by Bird—could no longer be trusted. Maskelyne, in consequence, ordered a six-foot mural circle from Troughton, but did not live to see it installed, and in 1816 this was supplemented by Troughton's transit instrument of five inches aperture and ten feet focal length.

The introduction of these two important instruments, and of other new instruments, together with new methods of observation, form one of the chief characteristics of Pond's administration. Under this head must be specially mentioned the introduction of the mercury trough, both for determining the position of the vertical, and for obtaining a check upon the flexure of the mural circle in different positions; and the use in combination of a pair of mural circles for determining the declinations of stars.

Another characteristic of his reign was that under him there was the first attempt to give the Astronomer Royal a salary somewhat higher than that of a mechanic, and to support him with an adequate staff of assistants. His salary was fixed at £600 a year, and the single assistant of Maskelyne was increased to six.

This multiplication of assistants was for the purpose of multiplying observations, for Pond was the first astronomer to recognize the importance of greatly increasing the number of all observations upon which the fundamental data of astronomy were to be based.

In 1833 he finished his standard catalogue of 1113 stars, at that time the fullest of any catalogue prepared on the same scale of accuracy. 'It is not too much to say,' was the verdict of the Royal Astronomical Society, 'that meridian sidereal observation owes more to him than to all his countrymen put together since the time of Bradley.'

A yet higher testimony to the exactness of his work is given by his successor, Airy.

'The points upon which, in my opinion, Mr. Pond's claims to the gratitude of astronomers are founded, are principally the following. First and chief, the accuracy which he introduced into all the principal 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 same authority eulogizes him further for his laborious working out of every conceivable cause or indication of error in his declination instruments, for the system which he introduced in the observation of transits, for the thoroughness with which he determined all his fundamental data, and for the regularity which he infused into the Greenwich observations.

One result of this great increase of accuracy was that Pond was able at once authoritatively to discard the erroneous stellar parallaxes that had been announced by Brinkley, Royal Astronomer for Ireland.

But Pond's administration was open, in several particulars, to serious censure, and the Board of Visitors, which had been for many years but a committee of the Royal Society, but which had recently been reconstituted, proved its value and efficiency by the remonstrances which it addressed to him, and which eventually brought about his resignation. His personal skill and insight as an observer were of the highest order; but either from lack of interest or failing health, he absented himself almost entirely from the Observatory in later years, visiting it only every ninth or tenth day. He had caused the staff of assistants to be increased from one to six, but had stipulated that the men supplied to him should be 'drudges.' His minute on the subject ran—

'I want indefatigable, hard-working, and, above all, obedient drudges (for so I must call them, although they are drudges of a superior order), men who will be contented to pass half their day in using their hands and eyes in the mechanical act of observing, and the remainder of it in the dull process of calculation.'

This was a fatal mistake, and one which it is very hard to understand how any one with a real interest in the science could have made. Men who had the spirit of 'drudges,' to whom observation was a mere 'mechanical act,' and calculation a 'dull process,' were not likely to maintain the honour of the Observatory, particularly under an absentee Astronomer Royal. Pond tried to overcome the difficulty by devising rules for their guidance of iron rigidity. The result was that after his resignation, in 1835, the First Lord and the Secretary of the Admiralty expressed their feeling to Airy, Pond's successor, 'that the Observatory had fallen into such a state of disrepute that the whole establishment should be cleared out.' A further evil was the excessive development of chronometer business, so as practically to swamp the real work of the Observatory, whilst the prices paid for the chronometers at this time were often much larger than would have been the case under a more business-like administration.

With all his merits, therefore, as an observer, the administration of Pond was, in some respects, the least satisfactory of all that the Observatory has known, and he alone of all the Astronomers Royal retired under pressure. He did not long survive his resignation, dying in September, 1836. He was buried by the side of Halley, in the churchyard at Lee.

Of Pond's instruments, the Observatory retains the fine transit instrument which was constructed by Troughton at his direction, and the mural circle, designed by Maskelyne, but which Pond was the first to use. Both of these have, of course, long been obsolete, and now hang on the walls of the transit room. The small equatorial, called, after its donor, the Shuckburgh equatorial, was also added in Pond's day, and though practically never used, still remains mounted in its special dome.

CHAPTER IV

AIRY

One hundred and sixty years from the day when Flamsteed laid the foundation stone of the Observatory, the Royal Warrant under the sign manual was issued, appointing the seventh and strongest of the Astronomers Royal, August 11, 1835. He actually entered on his office in the following October, but did not remove to the Observatory until the end of the year.

George Biddell Airy was born at Alnwick, in Northumberland, on July 27, 1801. His father was William Airy, of Luddington, in Lincolnshire, a collector of excise; his mother was the daughter of George Biddell, a well-to-do farmer, of Playford, near Ipswich. He was educated at the Grammar School, Colchester, and so distinguished himself there that although his father was at this time very straitened in his circumstances, it was resolved that young Airy should go to Cambridge. Here he was entered as sizar at Trinity College, and his robust, self-reliant character was seen in the promptness with which he rendered himself independent of all pecuniary help from his relatives. In 1823 he graduated as Bachelor of Arts, being Senior Wrangler and Smith's prizeman, entirely distancing all other men of his year. He had already begun to pay attention to astronomy, at first from the side of optics, to the study of which he had been very early attracted; a paper of his on the achromatism of eye-pieces and microscopes, written in 1824, being one of especial value. In 1826 he attempted to determine 'the diminution of gravity in a deep mine'—that of Dolcoath, in Cornwall. In the winter of 1823-24 he was invited to London by Mr. (afterwards Sir) James South, who took him, amongst other places, to Greenwich Observatory, and gave him his first introduction to practical astronomy. In 1826 he was appointed Lucasian Professor at Cambridge, and in 1828, Plumian Professor, with the charge of the new University Observatory. Prior to his election he had definitely told the electors that the salary proposed was not sufficient for him to undertake the responsibility of the Observatory. He followed this up by a formal application for an increase, which created not a little commotion at the time, the action being so unprecedented; and after a delay of a little over a year he obtained what he had asked for. The delay gave rise, however, to the remark of a local wit, that the University had given 'to Airy, nothing, a local habitation and a name.'

The seven years which he spent in the Cambridge Observatory were the best possible preparation for that greater charge which he was to assume later. When he entered on his duties the Observatory had been completed four years, but no observations had been published; there was no assistant, and the only instruments were a couple of good clocks and a transit instrument. But Airy set to work at once with so much energy that the observations for 1828 were published early in the following year, and he had very quickly worked out the best methods for correcting and reducing his observations. In 1829 an assistant was granted to him, in 1833 a second, and in the latter year Mr. Baldrey, the senior assistant, observed about 5000 transits, and Mr. Glaisher, the junior, about the same number of zenith distances.

A syndicate had been appointed at Cambridge for the purpose of visiting the Observatory once in each term, and making an annual report to the senate. A smaller-minded and less acute man than Airy might have resented such an arrangement. He, on the contrary, threw himself heartily into it, and made such formal written reports to the syndicate as best helped them in the performance of their duty, and at the same time secured for the Observatory the support and assistance which from time to time it required. On his appointment to Greenwich, he at once entered into the same relations to the Board of Visitors of that Observatory, and from that time forth the friction that had occasionally existed between the Board and the Astronomer Royal in the past entirely ceased. The Board was henceforth no longer a body whose chief function was to reprove, to check, or to quicken the Astronomer Royal, but rather a company of experts, before whom he might lay the necessities of the Observatory, that they in turn might present them to the Government.

Such representations were not likely to be in vain. For, as Mr. Sheepshanks has left on record—

'When Mr. Airy wants to carry anything into effect by Government assistance, he states, clearly and briefly, why he wants it; what advantages he expects from it; and what is the probable expense. He also engages to direct and superintend the execution, making himself personally responsible, and giving his labour gratis. When he has obtained permission (which is very seldom refused), he arranges everything with extraordinary promptitude and foresight, conquers his difficulties by storm, and presents his results and his accounts in perfect order, before men like ... or myself would have made up our minds about the preliminaries. Now, men in office naturally like persons of this stamp. There is no trouble, no responsibility, no delay, no inquiries in the House; the matter is done, paid for, and published, before the seekers of a grievance can find an opportunity to be heard. This mode of proceeding is better relished by busy statesmen than recommendations from influential noblemen or fashionable ladies.'

His first action towards the Board was, however, a very bold and independent one. He made strong representations on the subject of the growth of the chronometer business, which proved displeasing to the Hydrographer, Captain Beaufort, who was one of the official visitors, and by his influence the report was not printed. Airy '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.'

With the completion of arrangements which put the chronometer business in proper subordination to the scientific charge of the Observatory, Airy was free to push forward its development on the lines which he had already marked out for himself. To go through these in detail is simply to describe the Observatory as he left it. Little by little he entirely renovated the equipment. Greatly as Pond had improved the instruments of the Observatory, Airy carried that work much further still. Though he did not observe much himself, and was not Pond's equal in the actual handling of a telescope, he had a great mechanical gift, and the detail in its minutest degree of every telescope set up during his long reign was his own design.

In the work of reduction he introduced the use of printed skeleton forms, to which Pond had been a stranger. The publication of the Greenwich results was carried on with the utmost regularity; and, in striking contrast to the reluctance of Flamsteed and Halley, he was always most prompt in communicating any observations to every applicant who could show cause for his request for them.

It is most difficult to give any adequate impression of his far-reaching ability and measureless activity. Perhaps the best idea of these qualities may be obtained from a study of his autobiography, edited and published some four years after his death by his son. The book, to any one who was not personally acquainted with Airy, is heavy and monotonous, chiefly for the reason that its 400 pages are little but a mere catalogue of the works which he undertook and carried through; and catalogues, except to the specialist, are the dullest of reading. To enter into the details of his work might fill a library.

As Astronomer Royal he seems to have inherited and summed up all the great qualities of his predecessors: Flamsteed's methodical habits and unflagging industry; Halley's interest in the lunar theory; Bradley's devotion to star observation and catalogue making; Maskelyne's promptitude in publishing, and keen interest in practical navigation; Pond's refinement of observation. Nor did he allow this inheritance to be merely metaphorical; he made it an actual reality. He discussed, reduced, and published, in forms suitable for use and comparison to-day, the whole vast mass of planetary and lunar observations made at the Royal Observatory from the year 1760 to his own accession, a work of prodigious labour, but of proportionate importance. Airy has been accused—and with some reason—of being a strong, selfish, aggressive man; yet nothing can show more clearly than this great work how thoroughly he placed the fame and usefulness of the Observatory before all personal considerations. With far less labour he could have carried on a dozen investigations that would have brought him more fame than this great enterprise, the purpose of which was to render the work of his predecessors of the highest possible use. The light in which he regarded his office may best be expressed in his own words:—

'The Observatory was expressly built for the aid of astronomy and navigation, for promoting methods of determining longitude at sea, and (as the circumstances that led to its foundation show) more especially for determination of the moon's motions. All these imply, as their first step, the formation of accurate catalogues of stars, and the determination of the fundamental elements of the solar system. These objects have been steadily pursued from the foundation of the Observatory; in one way by Flamsteed; in another way by Halley, and by Bradley in the earlier part of his career; in a third form by Bradley in his later years; by Maskelyne (who contributed most powerfully both to lunar and to chronometric nautical astronomy), and for a time by Pond; then with improved instruments by Pond, and by myself for some years; and subsequently, with the instruments now in use. It has been invariably my own intention to maintain the principles of the long-established system in perfect integrity; varying the instruments, the modes of employing them, and the modes of utilizing the observations of calculation and publication, as the progress of science might seem to require.'

The result of this keen appreciation of the essential continuity of the Astronomer Royalship has been that it is to Airy, more than to any of his predecessors, or than to all of them put together, that the high reputation of Greenwich Observatory is due. Professor Newcomb, the greatest living authority on the subject outside our own land—and other great foreign astronomers have independently pronounced the same verdict—has said:—

'The most useful branch of astronomy has hitherto been that which, treating of the positions and motions of the heavenly bodies, is practically applied to the determination of geographical positions on land and at sea. The Greenwich Observatory has, during the past century, been so far the largest contributor in this direction as to give rise to the remark that, if this branch of astronomy were entirely lost, it could be reconstructed from the Greenwich observations alone.'

Early in 1836 Airy proposed to the Board of Visitors the creation of the Magnetic and Meteorological department of the Observatory, and in 1840 a system of regular two-hourly observations was set on foot. This was the first great enlargement of programme for the Observatory beyond the original one expressed in Flamsteed's warrant. It was followed in 1873 with the formation of the Solar Photographic department, to which the Spectroscope was added a little later.

Though he had objected strongly on his first coming to the Observatory to the excessive time devoted to the merely commercial side of the care of chronometers, yet the perfecting of these instruments was one that he had much at heart, and many recent appliances are either of his own invention or are due to suggestions which he threw out.

Much work lying outside the Observatory, and yet intimately connected with it, was carried out either by him or in accordance with his directions. The transit of Venus expeditions of 1874, the delimitation of the boundary line between Canada and the United States, and, later, that of the Oregon boundary; the determination of the longitudes of Valencia, Cambridge, Edinburgh, Brussels, and Paris; assistance in the determination of the longitude of Altona—all came under Airy's direction. Nor did he neglect expeditions in connection with what we would now call the physical side of astronomy. On three occasions, 1842, 1851, and 1860, he himself personally took part in successful eclipse expeditions. The determination of the increase of gravity observable in the descent of a deep mine was also the subject of another expedition, to the Harton Colliery, near South Shields.

But with all these, and many other inquiries—for he was the confidential adviser of the Government in a vast number of subjects: lighthouses, railways, standard weights and measures, drainage, bridges—he yet always kept the original objects of the Observatory in the very first place. It was in order to get more frequent observations of the moon that he had the altazimuth erected, which was completed in May, 1847. This was followed, in 1851, by the transit circle, as he had long felt the need for more powerful light grasp in the fundamental instrument of the Observatory. The transit circle took the place both of the old transit instrument and of the mural circle. Above all, he arranged for the observations of moon and stars to be carried out with practical continuity. The observations were made and reduced at once, and published in such a way that any one wishing to discuss them afresh could for himself go over every step of the reduction from the commencement, and could see precisely what had been done.

The greatest addition made to the equipment of the Observatory in Airy's day was the erection of the 12³/₄-inch Merz equatorial, which proved of great service when spectroscopy became a department of the Observatory.