PT. i. Astronomy and Geology compared. 41 



is to consider the Earth in what may be termed 

 its individual character, and to trace as far as is 

 practicable the past history of the planet from the 

 vestiges which are accessible to the researches of 

 man. Viewed under this aspect, the leading- 

 principle of the Astronomical system is reversed ; 

 fixity seems to govern the one, change appears to 

 guide the other. When we follow the Geologist in 

 his explorations, and penetrate those strata from 

 which he extracts his evidence of former conditions 

 of the surface, one truth appears to be evident that 

 the Earth has undergone a series of transformations. 

 Whatever uncertainty may prevail as to the date 

 and manner or the cause of these changes, the fact 

 seems to be indisputable. Primitive strata are 

 found at the bottom of the series in which no trace 

 either of animal or vegetable life can be discovered ; 

 over them are found more recent formations, 

 mounting in an ascending scale to the animal and 

 vegetable productions, which are preserved in them 

 in a fossil state, indicating a closer resemblance to 

 our condition. 



Different Greologists have assigned these changes 

 to different causes. Some, particularly the earlier 

 ones, have adopted what is termed the theory of 



