192 THE HISTORY OF SCIENCE 



place of the new planet, he began observations July 

 29. On August 4 in fixing certain reference points 

 he noted, but mistook for a star, the new planet. On 

 August 12, having directed the telescope in accord- 

 ance with Adams's instructions he again noted the 

 same heavenly body, as a star. Before Challis had 

 compared the results of the observation of August 

 12 with the results of an observation of the same 

 region made on July 30, and arrived at the inference 

 that the body in question, being absent in the latter 

 observation, was not a star but a planet, the prize of 

 discovery had fallen into the hands of another ob- 

 server. 



On August 31 had appeared Leverrier's third 

 paper, in which were stated the new planet's orbit, 

 mass, distance from the sun, eccentricity, and longi- 

 tude. The true heliocentric longitude was given as 

 326 32' for January 1, 1847. This determination 

 placed the planet about 5 to the east of star 8 of Cap- 

 ricorn. Leverrier said it might be recognized by its 

 disk, which, moreover, would subtend a certain angle. 



The systematic and conclusive character of Lever- 

 rier's research, submitted to one of the greatest acad- 

 emies of science, carried conviction to the minds of 

 astronomers. The learned world felt itself on the eve 

 of a great discovery. Sir John Herschel, in an ad- 

 dress before the British Association on September 

 10, said that the year past had given prospect of a 

 new planet. " We see it as Columbus saw America 

 from the shores of Spain. Its movements have been 

 felt trembling along the far-reaching line of our 

 analysis with a certainty hardly inferior to ocular 

 demonstration." 



