38 PROPER SUBJECTS OF GEOLOGICAL INQUIRY. 



to have undergone no alteration in their nature and quaUties; 

 but to have been submitted at their creation to the self-same 

 laws that regulate their actual condition, and to have con- 

 tinued subject to these law^s during every succeeding period 

 of geological change. The same elements also which enter 

 the composition of existing animals and plants, appear to 

 have performed similar functions in the economy of many 

 successive animal and vegetable creations. 



In tracing the history of these natural phenomena we 

 enter at once into the consideration of Geological Dyna- 

 mics, including the nature and mode of operation of all 

 kinds of physical agents, that have at any time, and in any 

 manner, affected the surface and interior of the earth. In 

 the foremost rank of these agents, we find Fire and Water, 

 — those two universal and mighty antagonizing forces, 

 which have most materially influenced the condition of the 

 globe ; and which man also has converted into the most 

 efficient instruments of his power, and obedient auxiliaries 

 of his mechanical and chemical and culinary operations. 



The state of the ingredients of crystalline rocks has, in a 

 great degree been influenced by chemical and electro-mag- 

 netic forces ; whilst that of stratified sedimentary deposites 

 has resulted chieffy from the mechanical action of moving 

 water, and has occasionally been modified by large admix- 

 tures of animal and vegetable remains. 



As the action of all these forces will be rendered most 

 intelligible by examples of their effects, I at once refer my 

 readers for a synoptic view of them, to the section which 

 forms the first of my series of plates.* The object of this 

 section is, first, to represent the order in which the succes- 

 sive series of stratified formations are on one another, almost 

 like courses of masonry ; secondly, to mark the changes 

 that occur in their mineral and mechanical condition; thirdly, 



* The detailed explanation of tliis section is given in the description of 

 the plates in vol. ii. 



