Ch. XVI.] OF THE PREVAILING THEORY. 387 



Such successive masses of transported debris have been ob- 

 served in every geological group, and appear to have been 

 produced by extraordinary movements of water, occurring at 

 distinct and remote periods, and which have been termed di- 

 luvial currents, or debacles. These catastrophes are now dis- 

 puted, the ordinary operations of water being deemed adequate 

 to explain all the phenomena. Let us, however, try this 

 opinion by applying it to the recent deposits resting 

 on the primary rocks of Cornwall ; and they are well 

 adapted for this purpose, because their materials may be 

 traced to the parent rocks, which form the more elevated 

 parts of the country. Rivers could not have brought 

 down these beds of debris, because the extent of land between 

 them and the summits of the hills is only sufficient to produce 

 small rivulets ; the bursting of lakes could not be their cause, 

 since the form of the surface is not in favour of such a view, 

 nor to the collection of large bodies of water; the waves of 

 the sea could not be the agent, because the deposits often rest 

 on vegetable strata, the remains of trees and plants, which 

 actually flourished on the places where they now repose. 

 Perhaps it may be argued that they were formed during the 

 emerging of the land from the ocean : if this be admitted, then 

 Cornwall has thrice subsided, and again arisen above the water, 

 and acquired a different sea-level at each catastrophe. But 

 even such operations are surely abnormal, differing much from 

 the constant and ordinary action of the sea; and we are only 

 desirous of establishing that water, as a transporting power, 

 has periodically acted with extraordinary violence. 



Now, between these debacles, we conceive that there were 

 successive periods of comparative rest, in which the ordinary 

 changes were gradually progressive. Thus, wherever 

 solid rocks or loose deposits were exposed, atmospheric and 

 aqueous degradations would be effected according to their 

 situations : their general surface, however, would be protected ; 

 the dry land by vegetation ; marshy places by the conjoint 

 action of plants and sediments ; the hollows, containing lakes, 



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