LECTURE XVII. 



ASTRONOMY. 







. SYSTEM OF THE UNIVERSE. 



ASTRONOMY is that science which treats of 

 the heavenly hodies. 



It is by means of this science that we know 

 the movement of those bodies, the duration of 

 their revolutions, whether apparent or real, their 

 position, their respective distances, &c. 



The origin of astronomy is very obscure, and 

 appears to be also very antient. " There is no 

 doubt," says Cassini *, " but that astronomy was 

 known almost from the beginning of the world. 

 It was not only curiosity which led man to the 

 study of astronomy, but it may be said that ne- 

 cessity itself obliged him to it. For if he did 

 not observe the seasons which result from the 

 apparent changes of the sun's place, it would 

 be impossible to succeed in the practice of agri- 

 culture and other useful arts." 



Astronomy, even if it could be considered as 

 useless to man, derives from its very nature a cer- 

 tain degree of dignity. But let it be remembered, 

 that upon it navigation, geography, and chrono- 

 logy greatly depend. By its aid man passes the 



* Memoirs of the Academy of Sciences, vol.vni. page 1. 



