190 THE HISTORY OF SCIENCE 



would account for the errors of the radius vector as 

 well as for those of heliocentric longitude. For Airy 

 this was a crucial question ; but to Adams it seemed 

 unessential, and he failed to reply. 



By this time a formidable rival had entered the 

 field. Leverrier at the request of Arago had un- 

 dertaken to investigate the irregularities in the 

 tables of Uranus. In September of the same year 

 Eugene Bouvard had presented new tables of that 

 planet. Leverrier acted very promptly and systemat- 

 ically. His first paper on the problem undertaken 

 appeared in the Comptes Rendus of the Academie 

 des Sciences November 10, 1845. He had submit- 

 ted to rigorous examination the data in reference 

 to the disturbing influence of Jupiter and of Saturn 

 on the orbit of Uranus. In his second paper, June 

 1, 1846, Leverrier reviewed the records of the an- 

 cient and modern observations of Uranus (279 in 

 all), subjected Bouvard's tables to severe criticism, 

 and decided that there existed in the orbit of Uranus 

 anomalies that could not be accounted due to errors 

 of observation. There must exist some extraneous 

 influence, hitherto unknown to astronomers. Some 

 scientists had thought that the law of gravitation 

 did not hold at the confines of the solar system 

 (others that the attractive force of other systems 

 might prove a factor), but Leverrier rejected this 

 conception. Other theories being likewise discarded 

 he asked : " Is it possible that the irregularities of 

 Uranus are due to the action of a disturbing planet, 

 situated in the ecliptic at a mean distance double 

 that of Uranus ? And if so, at what point is this 

 planet situated? What is its mass? What are the 



