2, THE MEDALS OF CREATION. Cuap. I. 
predominance of certain characters, to be used provisionally, 
as a convenient mode of classifying and generalizing the 
facts collected, whilst that knowledge is accumulating which 
in after times will reveal the nature and order of succession 
of the principal events in the earth’s physical history.* 
Dr. Buckland’s “ Bridgewater Treatise” (Vol. II. frontis- 
piece) contains a comprehensive Diagram of the rocks and 
strata of which the crust of the earth is composed ; it was 
drawn by the late Mr. Thomas Webster. 
* “Wonders of Geology,” p. 892. 
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