CELESTIAL MECHANICS 393 



tables furnished a sufficient means for carrying on the theory of 

 Jupiter. The work was completed not long before his death, and 

 science possessed a theory of the motion of that great planet carried 

 out in a remarkably homogeneous manner; even the theory of 

 Saturn, after a few additional computations by Gaillot, could be 

 considered satisfactory. 



In spite of the advances which Leverrier's work shows, astronomy 

 needed another giant to reach the standpoint which it has gained 

 during the last century; the name of this giant is Newcomb. A colos- 

 sal conscious force, the most comprehensive theoretic knowledge, an 

 acquaintance with observing material and its significance extending 

 to the smallest details, were necessary conditions for the undertaking, 

 immediately after Leverrier, of a revision of the planetary theory. 

 During the last half of the century a mass of observations, rich in 

 quantity and quality, had been gathered, which Leverrier had been 

 unable to use ; moreover, additional determinations of certain astro- 

 nomical constants gave values, which, in consideration of the great ac- 

 curacy now demanded, it was necessary to take account of in place of 

 those employed by Leverrier. Newcomb's great aim was to obtain a 

 system of astronomical constants and elements of motion which should 

 be as unified as possible, and should correspond with the progress 

 made in the art of observing. The theories of the planets Neptune 

 and Uranus which Newcomb published about 1870, but above all 

 his Catalogue of Fundamental Stars, seemed to be precursors of 

 the Astronomical Papers prepared for the use of the American 

 Ephemeris and Nautical Almanac. The catalogue mentioned is 

 especially important, since it forms, in a certain sense, an epoch in 

 the systematic treatment of observations, and the preparation of 

 them for the service of theory. What Newcomb did for the right 

 ascensions, Boss has done for the declinations. In the Astronomical 

 Papers we find, then, summa scientia astronomica, in all questions 

 that refer to the solution of the problem under discussion. The devel- 

 opments of the theories of the planets, while in agreement with the 

 general fundamental principles of celestial mechanics, are especially 

 adapted to the individual cases, varying in method as the problems 

 demand, and are always so explained as to keep clearly in view the 

 object to be attained. In this work, beside the name of Newcomb 

 shines that of the great mathematician, Hill, who has made avail- 

 able for the advancement of astronomical research the almost for- 

 gotten treasures of the immortal Gauss, and was the first to apply 

 successfully Hansen's method to the computation of the mutual 

 perturbations of Jupiter and Saturn. The astronomical papers are 

 thus valuable, not only on account of the results themselves, but also 

 by reason of the methods by means of which these were attained; 

 that is, in other words, these papers have brought celestial mechanics, 



