THE PLANET NEPTUNE. 17 



influence was insensible. He thus discovered some im- 

 portant terms which had been neglected by Laplace. 

 He then compared his theory with observation, and 

 proved conclusively that the observations of Uranus 

 could not be reconciled with the law of gravitation, 

 except by admitting some extraneous action. These re- 

 sults were communicated to the Academy of Sciences, 

 Nov. 10, 1845 ; and such was the reputation secured 

 by this and his preceding memoirs, that in January, 

 1846, he was elected to fill the vacancy which had oc- 

 curred in the Institute in the section of Astronomy, by 

 the death of Cassini. This memoir was but preliminary 

 to his grand investigation ; and it should be remarked, 

 that Mr. Adams had already deposited with the Astron- 

 omer Koyal at Greenwich, a paper containing the ele- 

 ments of the supposed disturbing planet, and agreeing 

 closely with the results which Le Yerrier subsequently 

 obtained. 



]^e Yerrier next proceeds to inquire after the cause 

 of the discovered irregularities. Is it possible that at 

 the immense distance of Uranus from the sun, the force 

 of attraction does not vary inversely as the square of 

 the distance? The law of gravitation is too firmly 

 established to permit such a supposition, until every 

 other resource has failed. Are these irregularities due 

 to the resistance of a rare ether diffused everywhere 

 through space? No other planet has afforded any in- 

 dication of such a resistance. Can they be ascribed to 

 a great satellite accompanying the planet ? Such a cause 



