626 ALLUVIA. 



selves affording, by their partial solution, that 

 cement by which they are united. 



The alluvial rocks which are formed by de- 

 positions from water, necessarily vary in dimen- 

 sion and disposition, as well as in situation, 

 according to circumstances which do not admit 

 of being here described. Those which originate 

 in the other causes just mentioned, also present 

 many variations, depending on circumstances 

 which may easily be apprehended. Thus they 

 are found in inland situations, or on sea shores, 

 or occupying portions, more or less extensive, of 

 the looser materials in which they are found. A 

 certain class of them form some of the varieties 

 of the veinstones mentioned in a preceding 

 chapter. 



In a geological view, they are in some other 

 respects very interesting ; as indicating those 

 actions of a corresponding nature, though much 

 more distant in point of time, which have led to 

 the consolidation of many of the looser strata of 

 sand and similar matters, and which, as they are 

 portions of the consolidated series of strata, have 



