44 



THE PLANET NEPTUNE. 



The following is the comparison between Le Yerrier's 

 predicted places and those resulting from Mr. Walker's 

 orbit during a period of 120 years. 



Thus, it appears, that during a period of 120 years, 

 the longitude of Neptune, according to Le Terrier's 

 computation, did not differ from that determined by Mr. 

 "Walker from the observations, more than 18'8, or about 

 one twentieth part of an entire circumference ; and during 

 the period in which the action of Neptune has been 

 clearly marked, that is, since 1812, the error of Le 

 Yerrier's theory has not exceeded 3'7. For 1690, the 

 theory is indeed very much at fault, but that is the 

 result of a comparatively small error in the positions 

 assigned during the present century. 



II. The error in the computed distance from the sun. 



