THE PLANET NEPTUNE. 51 



pect it. He assigned the most probable place of his planet 

 in longitude 325. He expressed the opinion that its 

 longitude would not be less than 321, nor more than 335. 

 But he adds, "If the planet should not be discovered 

 within these limits, then we must extend our search beyond 

 them}' 1 If he was sure of being able to find his planet 

 without a long-continued and laborious search, why did 

 he not borrow a telescope, and at once verify his own 

 predictions ? 



Nor had the astronomers of the rest of Europe much 

 higher faith than those of Paris. Professor Encke, in 

 announcing the discovery, characterizes it as "far ex- 

 ceeding any expectations which could have been previously 

 entertained" That Professors Airy and Challis, although 

 they were pretty well satisfied of the existence of a planet 

 yet undiscovered, regarded its exact place in the heav- 

 ens as extremely uncertain, is plain from their compre- 

 hensive plan of observation, viz., to sweep three times 

 over a belt of the heavens, thirty degrees in length, and 

 ten degrees in breadth, a plan which Professor Challis 

 states it would have been impossible for him to complete 

 within the year 1846. 



Do we then charge Encke and Airy with a want of 

 sagacity? By no means. On the contrary, we main- 

 tain that they had no reason to expect to find the planet 

 within one degree of the computed place. Le Vender's own 

 statement of the limits within which the planet should 

 be sought for, is sufficient proof of this. " L'incertitude 

 des donnees pourrait produire une incertitude de plus 



