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OBITUARY.

SIR GEORGE HOWARD DARWIN.

We regret to record the death of Sir George Darwin, Plumian Professor of Astronomy at Cambridge, which took place on Saturday afternoon. Two months ago he underwent an operation, and for a time it was reported that he might make a good recovery; but recently his strength failed, and it became known last week that there was room for little hope.

Seldom can a scientific career have been set in more appropriate surroundings than that which has just closed; "Born," to use a happy phrase coined for one of his brothers, "in the scientific purple," Sir George Darwin not only proved worthy of his imperial descent, but capable of extending the boundaries of Empire in new directions. The territories which he reclaimed from the vast ocean of the unknown lay in a direction in which his great father scarcely cast his eyes; and yet these noble additions gain greatly in interest from the harmonious relation to his father's conquests.

Charles Darwin had shown us how we may trace the patient growth of living things on the globe we inhabit. His son George aimed boldly at retracing the past history of the globe itself and of its neighbours in space; he brought to bear on his formidable task an indomitable courage and a patience like that of his father, or of Nature herself; and though by his comparatively early death we lose a worker whose hands had shown no signs of failing, and from whom much more was awaited, he leaves-behind him more than one monument which will endure.

George Howard Darwin, the second son of Charles Robert Darwin (author of the "Origin of Species") and- Emma, granddaughter of Josiah Wedgwood; was born at Down, Kent, on July 9, 1845. His father, who "most truly despised the old stereotyped stupid classical education. . .but yet had not courage to break through the trammels" (Life, vol. i., p. 381), in the case of his eldest son (whom he sent to Rugby), after much anxious thought placed his second son under the Rev. Charles Pritchard, afterwards Savilian Professor of Astronomy at Oxford (1870-1893). Pritchard's life as a schoolmaster at Clapham extended over 30 years (1833-1862); and in 1886, when his "old boys" entertained him at dinner, he wrote a brief account of the school, in which occurs the following:-

Another important element was derived from the sons of men at the head of the several branches of science and of the liberal professions. The names of Airy, Darwin, Gassiot, Grove (Sir W.), Hamilton (Sir W.), Herschel, Maurice, &c., became familiar in the roll-call.

Pritchard was about that time attracting the attention of thoughtful men by his pioneer work in scientific education. George Darwin gained a scholarship at Trinity College, Cambridge, was Second Wrangler and Smith's prizeman in 1868, and was elected Fellow of Trinity in the same year. The Senior Wrangler in his year, Mr. Fletcher Moulton (now Lord Moulton), in addition to early scientific eminence met with brilliant and well-known success at the Bar; the fourth Wrangler, Sir William Christie, was Astronomer Royal from 1881 to 1910. George Darwin, like Fletcher Moulton, chose the Bar as a career, and was "called" in 1874; but he soon returned to scientific investigation at Cambridge. He was elected Plumian Professor of Astronomy on the death of Challis in 1883. His Trinity Fellowship had expired in 1878, but he was re-elected in 1884, and remained a Fellow thenceforward.

In the same year he married Maud, daughter of Charles du Puy, of Philadelphia, U.S.A., and a niece of Lady Jebb; and he chose and adapted as residence Newnham Grange at the end of "the Backs." His children are two boys and two girls. His eldest son Charles followed his father as a scholar of Trinity in 1905, and graduated as Fourth Wrangler in 1909, the last year of the order of merit in the Mathematical Tripos.

METHODS OF RESEARCH.

George Darwin's chief work was done in his study, where he was constantly to be found in an arm-chair with his writing board resting across its arms, engrossed in toilsome arithmetical or analytical processes. He showed no great skill in invention of new machinery, or selection of elegant methods; his problems were solved by "frontal attack," by wearing down their resistance with sheer determination. He would attack, for instance, such a problem as this-Given the sun and a planet revolving round it, what will happen to a third body introduced within the range of their attractions? Will it revolve round the planet as a satellite, or round the sun as a second planet, or behave partly in both ways? Now, simple as this problem may seem to the uninitiated, it has been long known to defy solution exception a few very special cases, on which, therefore, attention has been concentrated. For bodies such as those of our solar system, which revolve in nearly circular orbits and afford other facilities for approximation, practical solutions have been found. But George Darwin was not content to study the present state of things; like his father, he wanted to know how it had come about, through past ages; and since the mathematicians had been unable to formulate the history by analysis, he entered upon the investigation in the other possible way - the step-by-step method. By laborious arithmetic he slowly pieced together the history following on selected conditions; then he varied the conditions slightly and started again, and so on continually feeling his way often almost in the dark, and stumbling at times on unexpected obstacles; naturally not knowing whither he was tending, and so being careful to leave the means of returning to any point at which he might choose the wrong path of several possible. in a paper read to the Royal Astronomical Society so lately as last June he recounts how one of these returns was rewarded. He had made several attempts to get an orbit of a particular kind, stopping the work when it was clearly going, off the track, but, "finally, for my own satisfaction, I completed the circuit of this discarded orbit, and found to my surprise that it belonged to a new and unsuspected class of periodic orbits."

TIDES AND THE HISTORY OF THE EARTH.

This work on orbits, however, successful and productive as it proved, does not strike the imagination so forcibly as the earlier work on the past history of the earth and the moon, which has played an important part in remoulding our ideas of the genesis of the universe at large. It had been realized that by drawing up tides on our earth the moon is not only arresting (by very slow degrees) the rotation of the earth, but also increasing her own distance from us in consequence; and these two changes must have been in progress as long as lunar tides have been in existence, that is to say, so long as there has been a moon separate from the earth. Looking backward, Darwin found (by mathematical analysis) the moon closer and closer to us, and our earth revolving quicker and quicker, until, in a distant past (for which he roughly assigned the date 57 million years ago) the earth and the moon formed one body rotating in about 51/2 hours. Some of the details of this work have been adversely criticized since it left the pen of the youthful investigator; but he recently took the occasion of the republication of his collected works by the Cambridge University Press to state his conviction (and he was always a candid critic of his own work) that the conclusions arrived at were substantially sound. But they are subject to a curious limitation.

On proceeding to extend the work of other systems of satellites Darwin found himself arrested by a totally different set of conditions; and he was forced to the conclusion that the

history of the earth-moon pair is quite unlike that of any other unit of our planetary system.

The great importance of the tides in our past history naturally drew Darwin's attention to their varied phenomena, and he quickly became a leading authority on the subject. Not only did he write technical reports of the highest value, but he produced a popular book on tides (the outcome of lectures delivered at the Lowell Institute in Boston), which has become a classic. Of his many activities in this field we can only give here two instances first, the beautiful experiments, conducted with the aid of his brother Horace, on the Lunar Disturbance of Gravity, reported to the British Association in 1881 and 1882, the forerunners of much important work elsewhere; and, secondly, the immense amount of work he cheerfully undertook in systematizing the collection of tidal observations, so that they might be more readily available not only for scientific progress, but also for the exact prediction so necessary to navigation.

HIS SKILL IN EXPERIMENT

Though Darwin's work was done almost entirely in the study, he by no means underrated the importance of practical work. He made some beautiful experiments on the pressure of a pile of sand, showing how astonishingly different it might be according to the manner of piling. The practical value of this work in formulating theories of earth pressure was acknowledged by the award of a medal by tho Institution of Civil Engineers. Such instances were, however, only too rare, and Darwin undoubtedly preferred to leave practical work to others. But when he was appointed Plumian professor in 1883, he immediately set about the provision of practical instruction in astronomy which had been in abeyance for some years. He appointed as his first demonstrator Mr. H. H. Turner, of Trinity, now Savilian Professor of Astronomy at Oxford, and the first pupil was Mr. J. W. F. Allnutt, who later gave much help to Professor Darwin in his researches. In recent years the teaching, of practical astronomy at Cambridge has been extended, by the joint action of the two Professors, to include geodesy, in the able hands of Mr. A. R. Hinks, Geodesy and tidal observation together form the practical side of George Darwin's work.

His devoted labour in respect of the latter is mentioned above; as regards geodesy, though he did no work in the field himself, he has been the representative of England on the International Geodetic Association, where his well-considered opinions have always been treated with the greatest respect from the first. In 1909 he conveyed the invitation to England, and took a large share in the meetings of the association in London and Cambridge.

No account of George Darwin's work would be complete without a reference to the influence which he himself never tired of acknowledging that of the late Lord Kelvin. The majority of his researches started from some fertile hint of his revered master, and were often guided later by his advice. Among these gratefully remembered experiences there was one of a unique kind, which Darwin related on the occasion of his receiving the Gold Medal of the Royal Astronomical Society in 1892. His work had led him to a conclusion so surprising that Lord Kelvin was frankly sceptical - would scarcely listen. But confidence in his result made Darwin persist in argument, and suddenly Lord Kelvin "saw the point, and was so delighted with it that I almost think he believed he had thought of it himself."

Personally Sir George was a most hospitable and pleasant companion, a man of the highest intellectual honesty, but widely tolerant of the diverging views of some of his friends. He took a very keen interest in the advance of Cambridge and of his own college, Trinity. Any progressive movement impelled his sympathy. His health was never robust, and he wisely never squandered his time on the details of academic reform, but for the principles he cared and for them he fought.

The funeral will be at 2 o'clock on Wednesday at Trinity College Chapel, and afterwards at Trumpington.