The daily Gate City. [volume] (Keokuk, Iowa) 1855-1916, 1858-11-19

tho growth Of its peculiar vegetation, than tt
the development of forests. 1t cannot fail
to strike the careful observer that where tht
prairie occupies the surface, the soil and SUI.
per6cial material have been 30 finely comni
nuted as to be almost Ia the state Of an i'm.
palpable powder. This u due partially ia
the peculiar nature OF the underlying rocks
| and the facility with which they undergo
| complete decomposition, and partly to the
mechanical causes which have acted during
| and since the accumulation of the sedmenta.
ry matter forming the prairie soil.
III we go TO a thickiy wooded region, like
that OF the northern peninsula Of Michigan,
and examine those portions OF the surface
which have not been invaded by the forest
we shall observe that the beds Of ancient
lakes, which have been filled up BY tho allow
est possible accumulation Of dotrital matter,
and are now perfectly dry, remain as natural
prAiries, and are not trespassed on by the
surrounding woods. We oan conceive OF NO
other reason for this than the extreme fne.
ness OF the soil which occupies these basins,
and which is the natural result OF the slow
and quiet mode in which they have been filed
up. The sides Of these deprcssions, which
were once lakes, slope very gradually up.
wards; and being covered with thick growth
OF vegetation, the material brought into them
must have been OF the finest possible kind, as
Is proved to have been the case by examina-
ton. Consequently, when the former lake
has become entirely filed up and raised above
the level OF overflow, We End it covered with
most luxuriant crop OF grass, forming the
natural meadows from which the first set
tiers are supplied with their winter store Of
fodder.
Applying these facts to the case of the
prairies OF larger dimensions farther south,
we infer, on what seem to be reasonable
grounds, that the whole region now occupied
by the prairies OF the northwest was once an
immense lake, in whose basin sediment OF
almost impalpablo fneness gradually aocu.
mnlated, under conditions which will be dis.
cussod In subsequent chapter that this ba-
sin was drained by the elevation OF the whole
region, but, at first, SO slowly, that the finer
PARTICLES OF the superficial deposits were not
washed away, but allowed to remain whore
they were originally deposited. After the
moro elevated portions of the former basin
had been laid bare, the drainage becoming
concentrated in comparatively narrow chan
neis, the current thus produced, aided per-
haps by more rapid rise Of the region, 40
CURED sufficient velocity to wear down through
the liner material on the surface, wash away
. portion Of il altogether, and mix the rest
so effeotually with the underlying drift mate
rails, or with abraded fragments of the rocks
in place, as to give rise to different charao.
ter OF soil in the vallies from that of the ele-
waited land. This valley soil, being much
less homogeneous in its composition and
containing larger proportion Of coarse ma.
terials than that OF the nplands, seems to
lave been adapted to the growth Of forest
vegetation; and, in consequence Of this, we
md such localities covered with an abundant
growth OF timber.
Wherever there has been variation from
the usual conditions Of soil, on the prairie or
IN the river bottom, there 10 a corresponding
change In the character of the vegetation
Thus, on the prairie, We sometimes meet with
ridges OF coarse material, apparently deposits
OF DRIFT, on which, from some local cause,
there has never been mn accumulation Of fue
sediment IN such localities we invariably
find growth of timber. This ia the origin
oil the groves scattered over the prairies, Tor
whose isolated position and peculiar circum-
stances OF growth We are unable to account 10
any other way.
The condition Of things in the river vallies
themselves seems to add to the plausibility Of
thi' shSoifs Al tuc ulStEICt WHICH We nave
more particularly examined, we have found
that where the rivers have worn deep and
comparatively narrow vallies bordered by
precipitous bluffs, there is almos. always q
growth of forest; but where the valley widens
out, and the bluffs become less conspicuous,
indicating q loss rapid erosion and currents
of diminished strength, there deposition has
taken place under circumstances favorable to
the accumulation Of prairie soil, and the
result has been the formation Of the ssbottom
prairie," which becomes 40 important fea-
ture Of the valliee Of the Mississippi and Mis-
souri, below the limits Of Iowa. Where these
bottom prairies have become, by any recent
change in the course of the river currents,
covered with coarser materials, a growth OF
forest trees may be observed springing up,
and indicating by their rapid deveiopm emit
the presence Of oongentsi soft.
nuas M