890 GEORGE WILLIAM HILL. 



aboriginal fire-making. He was an indefatigable collector and brought 

 together a valuable library and an important collection of archaeologi- 

 cal material, which he bequeathed to Harvard University, the Mu- 

 seum of Fine Arts, and the Boston Society of Natural History. 



A comparati\'ely full account of his life, with a list of his published 

 writings, was printed in the American Arithropologist, Vol. XV, 1913, 

 pp. 336-346. 



G. H. Chase. 



GEORGE WILLIAM HILL (1838-1914) 



Fellow in Class I, Section 1, 18G5. 



Hill's work on the lunar theory justly entitles him to a permanent 

 and important place in the history of celestial mechanics. In his 

 two papers, "Researches in the Lunar Theory," and "The Motion 

 of the Perigee of the Moon," he made contributions which have already 

 created a fundamental change in the methods of viewing the problem 

 of three bodies. In the first of these papers he outlined a plan for 

 dealing with the lunar theory as a practical problem and worked out 

 the first approximation. In the second paper the chief difficulty of 

 the second approximation is solved in a manner which shows Hill's 

 high capacity for algebraic analysis. This method, though based on 

 one by Euler, was given a form which was capable of development into 

 a complete theory. But to most students of the subject of celestial 

 mechanics his initiation of the idea of the periodic orbit in the former 

 of these papers is his greatest achievement. The great work of 

 Poincare which has pointed out new regions of research is based 

 mainly on this idea, and many others have followed in his footsteps. 

 Another feature of the memoir is the stress laid on the zero velocity 

 curve from which we may hope in the future to have some more exact 

 ideas as to the stability of planetary and satellite systems. 



Ten years of his life were spent in constructing theories of the 

 motions of Jupiter and Saturn, and in forming tables for the prediction 

 of the positions of those bodies. This work, although laborious and 

 carried out with great care and accuracy, contains little that is new. 

 Hansen's method is used with almost no change. In spite of the 

 success which attended his labors one cannot help a feeling of regret 



