622 ALLUVIA. 



rivers and estuaries, marine alluvia, alluvia of 

 descent, and un trans ported alluvia. 



A separate division must be formed to con- 

 tain the general alluvia, which occur in situations 

 where none of these causes can have acted, and 

 which appear to owe their origin, in many cases, 

 to deluges, apparently, of a temporary and par- 

 tial nature, in others, to that great event of the 

 same description recorded in sacred history. It 

 is extremely important to distinguish these from 

 the former, with which they have often been 

 confounded ; but to attempt even the slightest 

 sketch of this, would be to enter on a subject 

 foreign to the nature of this work. In all these 

 cases, the distinctions are chiefly, in many, purely, 

 of a geological nature. 



The extent, the depth, the forms, and the 

 connections of all these deposits, are so various, 

 that no description admissible in these prefatory 

 observations could convey an idea of them, and 

 they must consequently be reserved for their more 

 appropriate place in a System of Geology. It is 

 only necessary to observe in the briefest manner, 

 that their forms are under the daily influence of 



