RETROSPECT. 



In attempting to interpret the natural records 

 of the earth's physical history, the Geologist is 

 often in the condition of the Antiquary who en- 

 deavours to decipher an ancient manuscript, in 

 which the original characters are obscured and 

 partially obliterated by later superscriptions. It is, 

 indeed, frequently difficult, and sometimes impos- 

 sible, to determine the synchronism of those geo- 

 logical changes, of which the only indications are 

 insulated and but obscurely related phenomena. 

 Bearing in mind the caution of a distinguished 

 philosopher,* " that the language of theory can 

 never fall from our lips with any grace or fitness, 

 unless it appear as the simple enunciation of those 

 general facts with which by observation alone we 

 have become acquainted," we will take a retro- 

 spective view of what has been advanced, and 

 endeavour to deduce therefrom some general re- 

 sults as to the nature of those physical mutations, 



* Professor Sedgwick. 



