864 GEORGE HOWARD DARWIN. 



was appointed to the membership of a committee of the British 

 Association for the Advancement of Science appointed to consider 

 the subject. Nearly all the work of this committee was, however, 

 done by him, and his numerous papers on the subject exhibit the 

 large amount of time and labor which he gave in order that the methods 

 might be brought into a tractable and convenient form. 



All these papers meant heavy algebraical and numerical calcula- 

 tions, for Darwin was never contented until he had brought his 

 results into a concrete form. When they were nearly finished he 

 started to work on a problem which was equally laborious. Hill's 

 paper "Researches in the Lunar Theory" suggested the investigation 

 of the periodic orbits which could be followed by a small body under 

 the attractions of two larger bodies. Solutions of the differential 

 equations which could be conveniently adapted to numerical calcula- 

 tion appearing impossible, Darwin had recourse to numerical quad- 

 ratures and after some years of work was able to detect and draw a 

 large number of orbits, some of them of remarkable shape. In each 

 case the question of the stability of the orbit is considered. 



In spite of indifferent health Darwin was active in various directions. 

 As member of the Meteorological Council in England, and as the 

 British representative on the International Geodetic Association he 

 rendered important services to these bodies which were highly appre- 

 ciated. His presidency of the British Association in South Africa 

 gave evidence of his ability as a tactful and gracious speaker. As a 

 lecturer he was highly stimulating, and the volume, " The Tides," an 

 outcome of the Lowell Lectures delivered by him in 1897, is a master- 

 piece of exposition, free from technical language and mathematical 

 symbolism. His personality endeared him to his many friends, and 

 his death is felt by all those who knew him as a personal loss, in addi- 

 tion to creating a great gap amongst the ranks of science in which he 

 filled an honorable place. 



E. W. Brown. 



