THE PLANET NEPTUNE. 13 



ing body ? This idea was seriously entertained more 

 than twelve years ago by Bouvard, Hansen, Hussey, 

 Bessel, and some others. In a public lecture delivered 

 in the year 1840, Bessel stated, " I have arrived at the 

 full conviction that we have in Uranus a case to which 

 Laplace's assertion, that the law of gravitation entirely 

 explains all the motions observed in our solar system, is 

 inapplicable. We have here to do with discordances 

 whose explanation can only be found in a new physical 

 discovery. Further attempts to explain them must be 

 based upon the endeavor to discover an orbit and a 

 mass for some unknown planet, of such a nature, that 

 the resulting perturbations of Uranus may reconcile the 

 present want of harmony in the observations." 



Dr. T. J. Hussey, in 1834, proposed to compute an. 

 approximate place of the supposed disturbing body, and 

 then commence searching for it with his large reflector. 

 Mr. Airy, now Astronomer Royal of Great Britain, at 

 that time professor in Cambridge, pronounced the prob- 

 lem hopeless. His words were : "If it were certain that 

 there was any extraneous action upon Uranus, I doubt 

 much the possibility of determining the place of the 

 planet which produced it. / am sure it could not be done 

 till the nature of the irregularity was well determined from 

 several successive revolutions /" that is, till after the lapse 

 of several centuries. 



This deliberate opinion from one who, by common 

 consent, stood at the head of British mathematicians and 

 astronomers, would have deterred any but the most 



