112 THE ADVANCE OF SCIENCE 



as the work of a draughtsman who is at 

 once accurate and intelligent. 

 Astron- The determination of the existence of 



a new planet, Neptune, far beyond the 

 previously known bounds of the solar 

 system, by mathematical deduction from 

 the facts of perturbation ; and the immedi- 

 ate confirmation of that determination, in 

 the year 1846, by observers who turned 

 their telescox)es into the part of the heav- 

 ens indicated as its place, constitute a re- 

 markable testimony of nature to the valid- 

 ity of the principles of the astronomy of 

 our time. In addition, so many new as- 

 teroids have been added to those which 

 were already known to circulate in the 

 place which theoretically should be occu- 

 pied by a planet, between Mars and Jupi- 

 ter, that their number now amounts to 

 between two and three hundred. I have 

 already alluded to the extension of our 

 knowledge of the nature of the heavenly 

 bodies by the employment of spectros- 



