598 HISTORY OF GEOLOGY. 



of the actual facts of the earth's surface. The for- 

 mer, if perfected, would be a demonstrative science 

 dealing with general cases, the latter is an setio- 

 logical view having reference to special facts: the 

 one attempts to determine what always must be 

 under given conditions : the other is satisfied with 

 knowing what is and has been, and why it has 

 been : the first study has a strong resemblance to 

 mechanics, the other to philosophical archaeology. 



Since this portion of science is still so new, it is 

 scarcely possible to give any historical account of 

 its progress, or any complete survey of its shape 

 and component parts. I can only attempt a few 

 notices, which may enable us in some measure to 

 judge to what point this division of our subject is 

 tending. 



We may remark, in this as in former cases, that 

 since we have here to consider the formation and 

 progress of a science, we must treat as unimportant 

 preludes to its history, the detached and casual 

 observations of the effects of causes of change which 

 we find in older writers. It is only when we come 

 to systematic collections of information, such as 

 may afford the means of drawing general conclu- 

 sions ; or to rigorous deductions from known laws 

 of nature ; that we can recognize the separate 

 existence of geological dynamics, as a path of scien- 

 tific research. 



The following may perhaps suffice, for the pre- 

 sent, as a sketch of the subjects of which this science 



