ALLUVIUM. 
283 
tertiary formation. 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 filUng up 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 world, but only with the common 
interpretation of it. We are nowhere told when 
" the beginning" was, 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 inhabitants, 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 the 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-^ 
