The Cheyenne daily leader. [volume] (Cheyenne, Wyo.) 1870-1884, 1877-07-29
The Daily Leader.
sSOnicIal paper OF the City, County, Ter
ritory and United States.
The Origin of Prairies. 4.

The Origin of Prairies.
In paper in the American Natural
ist, Prof. j. d. Whitney, after showing
the insufficiency of the ordinary theor-
les toexplain why the prairies are noten-
croached upon by the bordering woods,
offers the following explanation of his
own:
LET us turn at present to the geo.
logical side of the investigation. The
whole of New England and New York,
and a large part of Ohio and Indiana,
together with the whole of Michigan
and of Northern Wisconsin, constitutes
a region over which the northern drift
phenomena liaye been displayed on a
grand scale. Consequently almost tho
whole of this area is covered with heavy
deposits of coarse gravel and coarse
boulder materials. These deposits, if
not at the surface, are near it, and the
finer material deposits on them, by
alluvial and other agencies, generally
form only thin covering for the coarse
deposits beneath. But as we go south
and west from the region indicated
above we find the underlying rock
the bedrock, - as the California miners
would call it-deeply covered with
loose materials, it is true, but we OBJ
serve that these are quite different in
character from what they are to the
north and east. We come to a region
where the drift agencies have been very
limited i'll their action. The bulk of
the superficial detrituS has been formed
from the decomposition of the underly-
ing rock, and this detritus has been but
t5tt rlN al &c
original position. If erratic deposits
exist, they are usually deeply covered
with finer materials derived from close
at hand. A great area exists in Wis
consn and Minnesota over which not
a single dirt pebble has ever been found,
either at the surface or at any depth be-
meath it. The strata have become
chemically disaggregated and dissolved
by the percolatiOn of the rain through
them, the calcareous matter has been
carried off in solution, and there is left
behind as residuum the insoluble mat
ter which the rock originally contained,
and which. consisting largely of silica
and silicate of alumina, forms by its
aggregation a silicious and clayey de-
posit of almost impalpable fineness. 1t
is this fine material which makes the
bulk of the prairie soil; and, as the
writer conceives, it is this fineness
which is especially inimical to the
growth of trees. Exactly as we see the
desiccated lakes in the midst of the
forests gradually filling up with finely
comminuted materials and becoming
covered with growth of grasses or
sedges, which is not afterward en-
croached on by trees, no matter
whether the ground becomes cOmplpte-
ly dry or whether it remains more or
less swampy, so we have the prairies,
which have certainly never at any time
been overspread with forests, and which
would always remain as they are, pro-
vided the climate underwent no radi-
cal change and they are not interfered
with by man. 1t is for the vegetable
Psychologist to say why this fineness of
soil is unfavorable to the growth of
trees; it is for the geologist and phys
ical geographer to set forth the facts
which they may observe within the line
of their own professional work.