376 LEADING AMERICAN MEN OF SCIENCE 



one probably not exceeded by any ever before attempted by an 

 astronomer, and yet Newcomb persisted, although in many cases 

 he was obliged to confine himself to a correction of the reductions 

 already made and published. The number of meridian observa- 

 tions on the sun, Mercury, Venus, and Mars alone numbered 

 62,030, and these were contributed by the observatories at Green- 

 wich, Paris, Konigsberg, Pulkowa, Cape of Good Hope, and 

 elsewhere. Says Newcomb: "The job was one with which I do 

 not think any astronomical one ever attempted by a single person 

 could compare in extent." 



It was this elaborate task of "bringing this great problem of the 

 solar system well-nigh to completeness of solution" that consti- 

 tuted Newcomb's life-work and in connection with which his 

 name will go down in history. It involved "an almost complete 

 reconstruction of the theories of the motions of the bodies of the 

 solar system" and "at its foundation the complete revision of the 

 so-called constants of astronomy." Such is the testimony of his 

 successor in the office of the Nautical Almanac, who further adds: 



"The distance of the earth from the sun; the displacement of the 

 earth in its orbit by the attraction of the moon ; the displacement of 

 the stars due to the motion of the earth combined with the motion 

 of light, which involves the velocity of light and space; the yearly 

 precession of the equinoxes; the obliquity of the ecliptic; the 

 dimensions and the masses of the planets; all had to be worked 

 into a homogeneous system to be used as a basis for the tables of 

 the sun and planets." 



The moon early attracted his attention and it held him until 

 the end. Almost his very first observations at the Naval Observa- 

 tory in Washington "showed that the moon seemed to be fall- 

 ing a little behind her predicted motion." He soon found that 

 other astronomers had found similar "inequalities" and therefore 

 he determined to ascertain the cause of this phenomenon. He 

 studied the records of other astronomers and after satisfying him- 

 self that the error had occurred prior to 1750, he searched the old 

 records of Europe and in Paris, and in Pulkowa found evidence 

 that traced the error back to before the year 1675, which in the 



