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 Devonian 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 calcareous 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. 



t 



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 



* Iu 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 



