of extensive Conglomoale and Gravel Deposits. 171 



materials available in the formation of extensively deposited 

 gravels and conglomerates, some greater and more general 

 force than the action of seas on their coasts, or rivers on their 

 beds, must collect them together. This force it seems natural 

 to seek in masses of water more or less voluminous according 

 to circumstances. To produce these at various times and in 

 greater or less abundance, the various dislocations of strata 

 everywhere so observable, seem adequate. It is now known 

 that mountains have been raised at different epochs, and that 

 horizontal strata, even those deposited at comparatively recent 

 geological epochs, have been shattered and broken into faults, 

 a large proportion of which are only covered by the gravels 

 that have been termed diluvium. Can we imagine that such 

 great convulsions and disruptions of our planet's crust could 

 have been unaccompanied by violent movements in the mass 

 of waters, and that debacles, as they are called, have not been 

 frequent and greai ? It seems but rational to infer that such 

 debacles or deluges must have more or less resulted from every 

 great convulsion, and have been more or less extensive ac- 

 cording to the power of the disrupting force. Such causes 

 could easily form the extensive gravel and conglomerate de- 

 posits ; we now observe, not only by their own destructive 

 power, but also by amassing all the river and sea-shore gravels 

 within their influence. 



According to this theory, the extent of gravels woukl cor- 

 respond with the extent of the disturbing forces, and would 

 be general where these forces were applied generally, and par- 

 tial where these forces were applied partially. 



Explanation oj Plate II. 



Fig. 1. Represents the Chesil Bank, and the soundings on either side of 

 the bani< ; and a small sliingle beach, near We3niouth, defending Lodnioor 

 Level from tiie sea. A small beach, called the Drift, is thrown up by the 

 sea, on the N.W. end of Portland, and nearly incloses a triangular space, 

 into which the sea enters at high water. Scale 2J miles to 1 inch. 



Fig. 2. The mouth of the Axe river, Devon, affords an example of a 

 shingle beach defending a low country from the sea, and of a river turned 

 from its direct course by a shingle bank, and forced to seek support from 

 a cliff' in order to escajjc into the sea. Scale 2 inches to 1 mile. 



Fig. 3. Example of a river deflected at a right angle from its course by 

 a bank thrown up by the sea. Scale 1 inch to 1 mile. 



Fig. 4. Delta of the Nile. Scale 70 miles to 1 inch. 



Z2 XXIV. On 



