Septemdek 17, 1900] 



SCIENCE 



355 



in an appendix to the Washington Obser- 

 vatians ior 1875. The memoir led to large 

 modifications in our estimation of the 

 value of Hansen's theory and it still must 

 serve as a foundation to all future investi- 

 gations in the subject. 



In 1877 Professor J. H. C. Coffin was 

 retired from the U. S. Navy on account of 

 age and thus the Ameri-can Ephemeris was 

 left without a head. Professor Newcomb 

 was appointed to the vacant place. He im- 

 mediately formed the grandiose scheme of 

 reforming nearly all the fundamental data 

 involved in the construction of an astro- 

 nomical ephemeris. One would have been 

 inclined to predict the failure or, at least, 

 only partial success of such a scheme ; but 

 Professor Newcomb, by his skilful manage- 

 ment, came very near to complete success 

 during his lifetime ; only tables of the moon 

 were lacking to the rounding of the plan. 

 It must, however, be noted that he was 

 fortunate in finding a few men ready to 

 hand in relieving him not only of the 

 drudgery of numerical calculation, but, in 

 some cases, of devising methods. To aid 

 mattei-s he founded a collection called The 

 Astronomical Papers of the American 

 Ephemeris to contain all the memoirs the 

 carrying out the scheme should give oc- 

 casion to. A large proportion of these 

 memoirs is the work of Professor New- 

 comb. So numerous are they that we must 

 be content with noticing only the more 

 striking and important ones. 



The transits of Mercury from 1677 to 

 1881 were discussed, with the principal re- 

 sult of coi'roborating Leverrier's assertion 

 of 40" in the secular motion of the peri- 

 helion unaccounted for. 



In the j^ears 1880-1882 Professor New- 

 comb made a determination of the velocity 

 of light by the Foucault method. The con- 

 struction of the instrument and the mode 

 of handling it enabled a very large angle 

 of deviation to be obtained; and thus an 



extraordinary degree of precision in the 

 result was hoped for. Although this hope 

 "was not completely fulfilled, nevertheless, 

 the concluded value is far in advance of all 

 previous determinations. 



Shortly after, Professor Newcomb ex- 

 haustively treated the transits of Venus in 

 1761 and 1769 with the object of obtaining 

 the constant of solar parallax and the posi- 

 tion of the node of Venus. 



In another memoir was derived the value 

 of the constant of nutation from material 

 afforded by observations with the transit 

 circles of Greenwich and Washington. 



Professor Newcomb deemed that im- \ 

 provements could be made in the mode of ' 

 deriving the periodic expressions needed in 

 the subject of planetary perturbations. 

 His method of treatment is elaborated in a 

 memoir in the American Journal of Math- 

 ematics, Vol. III., and, at greater length, 

 in a second memoir in the Astronomical 

 Papers, Vol. III. ; and, finally, application 

 is made to the four interior planets in a 

 third memoir contained in the latter vol- 

 ume. For certain long-period inequalities 

 in these planets it was found convenient to 

 employ expressions involving time-argu- 

 ments; this led to the composition of two 

 memoirs in Vol. V., of the same collection. 



The secular variations of the elements of 

 these planets are derived and the mass of 

 Jupiter determined from observations of 

 Polyhymnia in the two following memoirs 

 of the same volume. — i 



Professor Asaph Hall having found that 

 there was a rather rapid retrograde motion 

 of the line of apsides of Hyperion, Pi'o- 

 fessor Newcomb explained this from the 

 point of view of the variation of elements. 

 By an inadvei'tency at the very end of his 

 memoir he failed to obtain a correct value 

 for the ma-ss of Titan, the distui-bing body. 



The completion of these preliminary in- 

 vestigations enabled Professor Newcomb to 

 proceed at once to the composition of a me- 



