304 The Origin and Formation of Prairies. [ May, 
sippi river, in Whiteside county, was regarded by the observer as 
so extraordinary as to call for a special explanation. And yet on 
the prairies of Illinois, frequently lying on the surface and in the 
soil at all depths, are found numerous boulders of granite, syenite 
and trap rocks. On the surface they are found scattered from 
the hilltops to the very borders of the sloughs; and hidden in 
the ground they frequently prove a nuisance to the cultivator of 
the soil. Their presence in such situations cannot be reconciled _ 
with the notion that the soil is a lacustrine deposit. 
3. The general absence of fossils in the soil and subsoil of the 
high prairie lands is opposed to Lesquereux’s theory. In the 
Loess we find abundant fossils of land and fresh water shells. 
Such remains, too, sometimes occur in the deposits of the sloughs 
and marshes on the prairies; but these deposits are of later date 
than the soil of the higher grounds, and have frequently been 
formed as described by Lesquereux. If the prairie soil had been 
formed as he supposes, it would have afforded the most favorable 
conditions for the preservation of animal and vegetable organisms. 
“ At a depth of from one to three feet the mosses, conferve, and 
charas form a thick carpet which hardens, becomes consistent, 
like a kind of felt, and floating about six inches above the bottom, — 
is nearly thick enough to sustain the weight of a man. This 
carpet is pierced with holes where fishes pass to and fro; and the 
bottom under it is that fine impalpable clay, evidently a residue — 
of the decomposition of its plants.” We ought then almost any- 
where on these prairies, to find insect and leaf beds as rich as 
those of CEningen. But where now are those aquatic insects that 
people such waters; those land and fresh water mollusks; those 
numerous cray-fishes ; those leaves of plants that must have been 
buried there? Where are now those little fishes that passed to 
and fro through the holes in that mossy carpet? . So far as the 
writer knows, no such remains have been found. 
ae See 
4. The theory urged by the distinguished botanist requires US 4 
to suppose that these prairies have undergone a greater amount 
of denudation than would have been possible under the conditions 
supposed. He admits that the prairies must originally have been 
horizontal, and attempts to explain their present. undulating 
character by supposing that where we now find broad and Jevel 
sloughs, the soil has been removed by the gentle moveme 
water on its way to lower levels. The hills, however, rise frequ 
ly many feet, sometimes perhaps a hundred, above the leve 
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