December 13, 1907] 



SCIENCE 



811 



with them. Perhaps no observer in any 

 nation, unless it be Otto Struve, has con- 

 tributed so long and valuable a series of 

 observations with a single equatorial as is 

 embraced in the woi-k of Professor Hall. 



This work lay mainly in three directions : 

 first, planetary observations, consisting in 

 the main of determinations of the positions 

 of the satellites, with the consequent in- 

 vestigations of their orbits; second, obser- 

 vations of double stars with numerous in- 

 vestigations of the double star orbits ; third, 

 determinations of the stellar parallax. In 

 each of these fields of astronomical activity 

 Mr. Hall's work was of the highest value 

 and led not only to interesting observa- 

 tional results, but to most elegant discus- 

 sions of gravitational problems in the solar 

 and stellar systems. His observations, in 

 particular, of the system of the planet 

 Saturn, including those of the rings, have 

 been of primary importance in bettering 

 our knowledge of that interesting planet. 



In all this work Professor Hall showed 

 not only a high order of skill as an ob- 

 server, but he also developed a very high 

 order of ability in his gTasp of those mathe- 

 matical relations involved in the treatment 

 of the gravitational problems of our system 

 of planets and satellites. His papers con- 

 cerning the various problems arising out of 

 the motions of planets and satellites 

 brought him his highest recognition and 

 showed him to be a man possessing an order 

 of intellectual ability of exceptional char- 

 acter. It is not too much to say that he is 

 one of a group of Americans of not more 

 than a half dozen men at most who have 

 attained high rank as mathematical astron- 

 omers. 



The recognition of Professor Hall 's work 

 by various societies and governments is 

 most significant of the character of the 

 work itself. He received the gold medal 

 of the Royal Astronomical Society of Lon- 

 don, the Lalande prize of France, the 



Arago medal from the French Academy of 

 Sciences, and was made a knight of the 

 Legion of Honor. He was a member of 

 the more important scientific societies in 

 this country and abroad, being an honorary 

 member of the Royal Society in England 

 as well as of the French Academy and of 

 the Royal Academies of Russia and Ger- 

 many. As a member of the National Acad- 

 emy of Sciences of America he served for 

 many years as secretary and later as its 

 vice-president. He received honorary de- 

 grees from many colleges and universities, 

 amongst others the degree of LL.D. from 

 Yale and the same degi-ee from Harvard 

 at the celebration of its two hundred and 

 fiftieth anniversary. 



Retiring from the Naval Observatory at 

 the age of sixty-two, in accordance with 

 naval regulations. Professor Hall continued 

 his work for some years at the observatory 

 in order to complete those matters upon 

 which he was particularly engaged. For 

 some years after he was in charge of the 

 observatory at Madison, Wisconsin, and in 

 1896 became a member of the faculty of 

 Harvard University with the title of pro- 

 fessor of mathematics, which he retained 

 until 1901. 



Professor Hall's first wife, Angeline 

 Stickney HaU, died in July, 1892. Of this 

 marriage four sons survive. In October, 

 1901, he married Mary B. Gothier, of 

 Goshen, Conn., who survives him. 



Professor Hall numbered amongst his 

 friends the leading scientific men of Eu- 

 rope and of America. His correspondence, 

 running back for more than fifty years, 

 would form of itself an interesting account 

 of the astronomy of his day. He was in 

 temperament, in devotion, in the simplicity 

 and singlemindedness of his life, a true 

 man of science. For him no distractions 

 of social recognition or money-making 

 served to withdraw his attention from the 

 science to which he had given his life. No 



