THE PLANET NEPTUNE. 47 



sell's observations, is T T!O-O-- The former value comes 

 fairly within the limits assigned by Le Terrier, the latter 

 somewhat exceeds them. 



On the whole, we must conclude that the orbit of Nep- 

 tune agrees with the orbit predicted by Le Yerrier, very 

 nearly within the limits which Le Yerrier now assigns, 

 upon the supposition of an uncertainty of 5' in the data 

 since 1781. But these limits, with respect to distance 

 and time of revolution, are very different from those as- 

 signed before the discovery of the planet. The orbit of 

 Neptune is not included within the limits which Le Yer- 

 rier then assigned ; and it is a legitimate inference, from 

 his own premises, that Neptune is not the planet whose 

 existence he announced. 



It should also be borne in mind that Professor Peirce 

 has shown that Neptune reconciles all the observations 

 of Uranus since 1781 within 3", and that the greatest error 

 of any of the ancient observations according to his theory 

 is 8" ; thus proving that Le Yerrier's suspicion of the ex- 

 istence of a planet beyond Neptune, and of an error in 

 the mass of Saturn is unfounded. The data, therefore, 

 instead of being uncertain to one tenth of their whole 

 amount, were generally reliable within one sixtieth of 

 their value ; and Le Yerrier's elements are erroneous 

 to an extent far beyond the one sixtieth of their value. 



It will naturally be asked, how has it happened that 

 two astronomers, Adams and Le Yerrier, have arrived, 

 by independent computations, at almost identically the 

 same result, and have made such mistakes with respect 



