414 



NATURE 



[December 12, 1912 



and to absorb whatever of scientific interest was 

 g-oing: on, lie was certain to find his way to Newn- 

 ham Grange, to compare impressions on tidal and 

 cosmical theory and to concert plans for future 

 action. So thoroughly was Darwin from the first 

 immersed in and a partner of Kelvin's work on 

 these subjects, that the necessary rewriting, for the 

 second edition, of the large section of Thomson 

 and Tait's "Natural Philosophy" which deals 

 with tides and their cosmical relations, was con- 

 fided entirely to his hands. 



In i8g8 he supplemented this work by publish- 

 ing a non-mathematical treatise on the tides and 

 kindred phenomena in the solar system, which 

 was developed from a course of Lowell lectures 

 delivered at Boston, and has taken rank with the 

 semi-popular writings of Hehnholtz and Kelvin as 

 a model of what is possible in the exposition 

 of a scientific subject ; it has accordingly been 

 translated into many foreign languag'es. The 

 preparation of a new edition of this book, ex- 

 panded and in part rewritten to include recent 

 developments, was one of the last works of his 

 life. 



His studies in astronomical evolution necessarily 

 required him to push the history of the motions 

 of the planetary bodies back into the past, far 

 beyond the times for which the usual practical 

 approximations of gravitational astronomy are 

 suitable or valid. To this end he began to apply 

 a process of stcp-by-step plotting to the determina- 

 tion of orbits in the classical problem of three 

 bodies, — essayed in simpler cases by Lord Kelvin, 

 but in its adequate use laborious, and demanding 

 skill in arrangement of arithmetical processes ; 

 this work culminated in an extensive memoir in 

 "Acta Mathematica" in i8g6. The maps of 

 families of orbits there published attracted the 

 attention of other mathematicians. In particular, 

 Poincare — utilising the general mode of dis- 

 crimination and classification which he had already 

 employed with signal success in Lord Kelvin's 

 and George Darwin's problem of the forms pos- 

 sible for fluid rotating planets — pointed out the 

 necessary existence of some intermediate classes 

 that had escaped the analysis. And S. S. Hough, 

 H.M. Astronomer at the Cape, who had in his 

 Cambridge days collaborated with Darwin in tidal 

 theory, followed with a memoir devoted to fuller 

 developments. This fascinating subject con- 

 tinued to occupy Darwin's attention up to the end 

 of his life ; one of his last public appearances in 

 London was to communicate a paper on it to the 

 Ro\al Astronomical Society. 



His thorough familiarity with the methods of 

 reducing to mathematical order the tangled data 

 of tidal observation marked out Darwin as a 

 desirable expert guide in the national meteoro- 

 logical service ; for much was hoped for meteoro- 

 logj' thirty years ago from the practical application 

 of harmonic analysis to the voluminous records of 

 barometer and thermometer. Accordingly the 

 Royal Society, which then had control of the ser- 

 vice, nominated him a member of the Meteoro- 

 logical Council soon after his return, to Cambridge. 



NO. 2250, VOL. go] 



When that Council was rearranged as a Com- 

 mittee under the Treasury a few years ago, he 

 became one of the two representatives v^^hom tlie 

 Royal Society was requested to nominate to the 

 new body ; and he continued to render valuable 

 service in this capacity until the end. 



The earliest ot topographic surveys, the model 

 which other national surveys adopted and im- 

 proved upon, was the Ordnance Survey of the 

 United Kingdom. But the great trigonometrical 

 survey of India, started nearly a century ago, and 

 steadily carried on since that time by officers 

 of the Royal Engineers, is still the most important 

 contribution to the science of the figure of the 

 earth, though the vast geodetic operations in the 

 United States are now following it closely. The 

 gravitational and other complexities incident on 

 surveying among the great mountain masses of 

 the Himalayas early demanded the highest mathe- 

 matical assistance. The problems originally at- 

 tacked in India by Archdeacon Pratt were after- 

 wards virtually taken over by the Royal Society, 

 and its secretary. Sir George Stokes, of Cam- 

 bridge, became from 1864 onwards the adviser 

 and referee of the survey as regards its scientific 

 enterprises. On the retirement of Sir George 

 Stokes, this position fell very largely to Sir George 

 Darwin, whose relations with the India Office on 

 this and other affairs remained close, and very 

 highly appreciated, throughout the rest of his life. 



The results of the Indian survey have been of 

 the highest importance for the general science of 

 geodesy, and well-deserved tributes have been 

 paid to them by Helmert, of Berlin, and other 

 chief exponents of the science. It came to be felt 

 that closer cooperation between different countries 

 was essential to practical progress and to co- 

 ordination of the work of overlapping surveys. 

 .\ccordingly, about fifteen years ago the Inter- 

 national Geodetic Association was established, 

 through scientific and diplomatic influences, to 

 take cognisance of all problems of refined surveys 

 and triangulations, and other investigations re- 

 lating to the form of the earth, in which inter- 

 national cooperation is essential to complete 

 results. Sir George Darwin was appointed by the 

 Foreign Office, on the advice of the Royal Society, 

 as the British representative on this important 

 international body; and its work was henceforth 

 one of the main interests of his life. It came to 

 the turn of England to receive the triennial 

 assembly in the year 1Q09, and a very successful 

 meeting at London and Cambridge was organised 

 mainly by his care. He was preparing to go to 

 the meeting of the association in Hamburg last 

 September wlien his fatal illness supervened. 



An important public service has been rendered 

 in this country for many years by the Cambridge 

 University Press, through the application of its 

 resources to the publication in definitive collected 

 form of the works of the great men of science 

 whom this nation has produced, thereby sustain- 

 ing the national credit in a way which in other 

 countries is promoted mainly by Government sub- 

 sidy. The collected papers of Sir George Stokes, 



