PT. i. Astronomy and Geology compared. 3 



they are secondary and subsidiary in their relations 

 to them. 



For example, the two sciences of Navigation and 

 of Greography are largely indebted to Astronomy, 

 which points out to them the modes, by the means 

 of celestial observations, of verifying all the positions 

 on the earth's surface ; but Greography and Naviga- 

 tion only borrow from Astronomy the means by which 

 they make these calculations, they add nothing to 

 them, they only derive aid from them, they originate 

 nothing. 



Although, as I have remarked, there is a close 

 connection, and, if I may use the expression, a sym- 

 pathy, between these two great sciences, yet, on the 

 other hand, there are several important differences 

 between them which it may be interesting to observe. 

 Let us endeavour to enumerate some of the most 

 striking and remarkable. 



First. The dates of their birth differ as widely as 

 possible. Astronomy is about the oldest ; Greology 

 is nearly the youngest and last in the whole circle of 

 the sciences. We must carry our knowledge of the 

 commencement of Astronomy to the very beginning 

 of the historic period ; we must mount up to the 

 days of the Assyrian monarchy, and the periods of the 



B 2 



