619 



ALLUVIA. 



THE history of the greater number of these 

 deposits is of the most interesting kind, but is so 

 purely matter of geological inquiry as to be in- 

 admissible in this work. There are two distinct 

 divisions of substances comprised under this 

 head, the loose and the solid ; both of them pos- 

 terior to the latest indurated strata, and the latter, 

 evidently more recent than the former. A few 

 words must suffice respecting both. 



Alluvial, unconsolidated deposits, occur in 

 various situations, bespeaking, in many, im- 

 portant differences of origin. 



Where they are found in vallies through 

 which rivers flow, they generally arise from the 

 abrasion of the channels in which these run ; 

 and more particularly, from the wear of the 

 higher rocky hills that form their sources and 

 contain their springs. They originate in the 



