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ALLUVIAL DEPOSITES. 
ers. They are, of course, made up of the finest and 
richest portions of every soil over which the water 
has passed. We accordingly find such a formation 
distinguished for its fertihty, as the banks of the 
Nile, the Mississippi, the Ohio, and the Connecticut. 
We find a strip of such deposites along the banks of 
almost every stream, of greater or less width ; also 
on the shores of lakes and of the ocean. Swamps 
also consist of alluvial soil, washed thither by rains 
and brooks, and generally abound in vegetable mat- 
ter, which might be employed to great advantage 
as a manure. 
Alluvial deposites are sometimes stratified, pre- 
senting distinct layers, wavy, horizontal, or oblique, 
marking successive depositions from water. Mr. 
Lyell states that " alluvium is strewed alike over 
inclined and horizontal strata and unstratified rocks ; 
is most abundant in valleys, but also occurs in high 
platforms, and even in lofty mountains ; that of the 
higher grounds usually differing from that found at 
lower levels." 
It is, however, customary for geological writers 
to refer beds of gravel, or of stones more or less 
rounded, that are found in inland districts, as well 
as the large and detached masses of rock called 
bowlders or erratic blocks, to the operation of some 
great convulsion, by deluges or inundations, more 
powerful than any causes at present in operation, 
and to call such deposites diluvium or diluvial depos- 
ites. It is distinguished from alluvium by the cir- 
cumstance that it is much coarser, being made of 
large pebbles or rounded stones, mixed with sand 
-and fragments of every size, often piled up in 
rounded hills of considerable height, and under such 
circumstances as would preclude th-e possibility of 
its resulting from existing streams. We find it 
covering the highest mountains and spread over 
every kind of rock ; in short, so disposed as to 
prove very conclusively that at some former period 
