1876.] Plain, Prairie, and Forest. 663 
ocean. Thus we find the distribution of forest and prairie in 
Wisconsin to be most intimately connected with the nature of 
the soil and the geological conditions under which this has been 
formed, while it has been clearly shown that climatic conditions 
were either absolutely null in their action or else entirely second- 
ary to those other more potent ones which have been designated. 
Were there space enough, it would be possible to show, with 
abundant detail of description, how, all over the prairie region, 
the characters of the soil and the surface harmoniously combine 
to favor or repress the growth of forests, regardless of the amount 
or distribution of the atmospheric precipitation. A thorough 
working out of the surface geology of Missouri or Arkansas 
would especially well illustrate the correctness of the statements 
which have been here advanced, and the inferences which have 
been drawn from them. 
It remains to say a few words in regard to the views of Mr. 
Lesquereux. He, if we have correctly apprehended his theory, 
ascribes the existence of the prairies almost exclusively to the 
character of the soil. But he conceives this unfittedness for 
tree-growth to be, in some way not clearly apprehended by i 
Writer, due to the “ agency and growth of a peculiar vegetation. 
we are not mistaken, the essential points of the theory of Mr. 
Lesquereux’ are —and, as far as possible, we will use his own 
Words in setting it forth — “ that all the prairies of the Missis- 
sippi Valley have been formed by the slow recess of sheets of 
water of various extent, first transformed into swamps and by 
and by drained and: dried ;” the soil thus formed “is neither 
“Peat nor humus, but a black, soft mold, impregnated with a 
large proportion of ulmie acid, produced by the slow decomposi- 
tion, mostly under water, of aquatic plants, and thus partaking 
as much of the nature of the peat as of that of the true humus ; 
these plants “ contain in their tissue a great proportion of lime, 
alumina, silica, and even of oxide of iron, the elements of clay. 
Moreover, this vegetation of the low, stagnated waters ape 
Prodigious quantity of small mollusks and infusoria, whose she 
and detritus greatly add to the deposits. The final result of 
‘the decomposition of the whole matter is that fine clay of the 
subsoil of the prairies, which is indeed truly impalpable, when 
dried and pulverized and unmixed with sand.” 
1Mr. Ga i ournal of Science (3), ii. 127) that in 
Santo tg ths iias Merrit sie sharply defined, and correspond in the 
main with certain geological features.” 
