ALLUVIUM. 



283 



tertiary forma'tion. This must have required an 

 immense period, because it is, perhaps, on an aver- 

 age, 150 feet thick ; and if we judge from the present 

 rate of filUngup of our lakes with mud, it must have 

 required many thousands of years. This, however, 

 does not clash with the Scripture account of the 

 creation of the v/orld, but only with the common 

 interpretation of it. We are nowhere told when 

 " the beginning" w^as, when God created the earth ; 

 only that it was created in the beginning. How 

 long a time was passed over in silence between 

 " the beginning" and that period when the earth was 

 reduced to its present state, and peopled with its 

 present races of inhabit'ants, we are not informed. 



Alluvium, 



The surface of the earth, as we have already sta- 

 ted, is constantly undergoing changes. Rocks are 

 crumbling; mountains disintegrating ; hills wearing 

 away; the banks of rivers, lakes, and the ocean dis- 

 appearing; and the sand, gravel, clay, loam, and 

 mud, when deposited from all these sources, con- 

 stitute alluvium. We find such deposites chiefly on 

 the banks of rivers, lakes, and the sea, in swamps 

 and low grounds ; and they constitute ihe richest 

 and most valuable soil for the agriculturist. These 

 alluvial tracts are, indeed, composed of the very 

 finest materials, such as, from their suspension in 

 water, would be carried to great distances, and their 

 effect in enriching the soil may be estimated from 

 the influence of th^ annual overflow of the Nile, 

 which is looked for with the greatest anxiety by the 

 inhabitants, as its absence is a pretty sure indica- 

 tion of a famine. In this country we have rich 

 alluvial tracts bordering most of our rivers and 

 streams, such as the Connecticut, the Merrimack, 

 the Housatonic, the Hudson, the Susquehanna, the 

 Delaware, the Potomac, the Ohio, the Mississippi, 

 the Wabash, the Illinois, the Missouri, the Red Riv- 



