IOWA, AND WAPSINONOX RIVERS. 81 
these limestones are concealed, wholly or partially, by extensive deposits of drift. 
Indeed, they appear mostly only in low ledges, near the water-courses. 
East of the Mississippi, this belt was traced as far as Rock River; and it doubtless 
extends still farther west,* as limestones of the same geological era show themselves 
on the shores of Lake Michigan in the vicinity of Milwaukie. | 
Neither on the St. Peter's or its tributaries were any rocks discovered that could 
be referred to the period of either the Upper Silurian, Devonian, or Carboniferous 
Systems. 
Three-quarters of a mile below the mouth of the Waraju River, there is a light 
gray limestone (containing at least ninety per cent. of carbonate of lime, and only 
a fractional per cent. of magnesia), which rests apparently conformably on the 
sandstones of Formation 1. This limestone differs in its appearance and composi- 
tion from any of the beds of Formation 2, observed elsewhere in the Minnesota 
country, and resembles more those of the Devoriaii System found in the southern 
portion of the District; but since no fossils were detected in this calcareous for- 
mation, we are not able to furnish any conclusive evidence of its belonging to 
that system of rocks. This is the purest caleareous rock discovered as yet in the 
Chippewa Land District, north of latitude 43°, and will become an article of value 
to the inhabitants of that region of country, where limestones containing a large per- 
centage of magnesia are so universal. 
SECTION V. 
ITS PHYSICAL AND AGRICULTURAL CHARACTER. 
On leaving the northwestern margin of that portion of the Illinois coal-field, which, 
on the west side of the Mississippi, juts into Iowa, in the vicinity of Muscatine, a 
sudden change is observable, not only in the character of the soil, but also, to some 
extent, in the climate. The soil which overlies the sandstones of the coal-measures 
is of that warm, quick, siliceous, porous character, which rapidly advances vegeta- 
tion, but is apt to leave it in a parched condition, during the droughts of summer 
or autumn; while, immediately north of the mouth of Mud Creek, the stiff, dark, 
calcareous soil, marking the transition to the limestones of Cedar Valley, appears. 
Though less forcing in its character than the other, this soil is much richer and 
more retentive ; storing up the successive acquisitions and infiltrations from organic 
decomposition, until the proportions of geine, humus, and other organic principles 
rise from ten sometimes even to thirty per cent. For wheat and small grain gene- 
rally, this soil is well adapted. 
Though the valley of Cedar River cannot boast the dense forests of Indiana or 
* In Missouri, this formation was traced, reappearing, for a very limited space, in the valley of the Aux 
Vasses, in Calloway County ; ; skirting, for a short distance, one of the southern promontories of the Iowa 
and Missouri coal-field, in close proximity to the great uplift of Magnesian limestone, of Silurian date, in 
the same vicinity. It has, probably, a considerably greater range in this locality, than here ascertained 
and laid down by me. 
11 
