III. GEOGENY. 



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184. We may inquire into the manner in which the crust 

 of the earth has attained its present state, by studying the 

 phenomena which are taking place under our own eyes. In 

 this examination we discover the agency of certain proximate 

 causes, and by a comparison of the formations which are 

 certainly produced by them, with those of more ancient date, 

 we infer from the analogy of structure and character, that 

 the same causes were also in action at more remote epochs 

 of the earth's geological history. We may thus determine 

 to what description of action the several ancient formations 

 were probably due, and we may, in one instance at least, go 

 back a step further, and inquire, whether in the known laws 

 of physical science we can discover the reason of the preva- 

 lence of the action of one of these proximate causes. The 

 same physical laws may be applied in the progress of the 

 inquiry, to explain the reason why formations to which the 

 same proximate cause can with certainty be assigned, differ 

 in character from each other ; and the spirit of inductive in- 

 vestigation will enable us to reach, by analogy, the agent 

 which was concerned in formations whose origin cannot be 

 otherwise ascertained. 



185. We have ranked first among modern formations 

 those which are of a vegetable origin : with these may be 

 classed the coralline shoals and islands, and we thus infer, 

 that the birth, growth, death and decay of organized beings 

 is a cause whose action is to be sought among the ancient 

 formations. 



