56 



PROTOZOIC ROCKS 



far and wide with beds of sand, once the materials of hills, of which either no 

 vestiges now remain, or which are gradually denuding and crumbling before the 

 slow but sure influence of atmospheric vicissitudes. Rocks, whose particles are 

 held together so loosely that they may be crumbled between the hands, cannot be 

 expected to resist degrading forces that have ground to powder, corroded, and 

 swept away hundreds of feet of solid limestone. The rounded outlines of the 

 distant hills and scooped-out valleys bear witness to the extensive denudation of 

 the elevated lands of this region. 



The Chippewa River, in making a sudden sweep, has laid bare, on its north side, 

 as shown on the right hand of the sketch, a bank of light-yellow sand, to the depth 

 of about forty feet. Its appearance is that of an amphitheatre of more than a 

 quarter of a mile in length, crowned only with shallow vegetable mould of a few 

 inches in depth ; and here and there may be seen, at intervals, for several feet down 

 the cut, dark bands, marking as many distinct soils, which once occupied the sur- 

 face, and have successively been covered by drifting sand, as it shifted and was 

 blown about by the winds over the plain. 



The analysis of the soil* of this part of the Chippewa River gives ninety-three per 

 cent, of insoluble matter, which is chiefly a fine white sand, with only two per cent, 

 of organic matter, less than four per cent, of soluble saline matter, consisting chiefly 

 of oxide of iron and alumina, with only a trace of calcareous earth. A soil so 

 unstable, so arid, and so deficient in fertilizing ingredients, cannot be very attractive 

 to the agriculturist. Locally, however, the soil of F. 1 produces better than its 

 appearance at first indicates, on account of an admixture of lime, derived from the 

 intercalated calcareous beds, the overlying magnesian limestone, or from drift. A 

 belt of country, much of the same character, extends from the Menominie or 

 the Red Cedar branch of the Chippewa, towards Black River and Prairie a la 

 Crosse River. The average width of the tract may be forty or fifty miles ; its course 

 for about seventy miles is nearly parallel with the Mississippi, and distant from it 

 some twenty to thirty miles. From Prairie a la Crosse River it diverges more to 

 the east, crossing the Wisconsin between Point Bass and the Dalles. From the 

 Menominie, north, this character of country takes a north-northeasterly course, 



* A sandy soil, collected nine miles above the mouth of the Chippewa, in the region of F. 1, gave, from 



one hundred parts, as follows : — 



Water, .......... 1-02 



Organic matter soluble in carbonate of ammonia, .... 1-75 



Organic matter insoluble in carbonate of ammonia, .... -25 



Insoluble silicates, . . . . . . . .93-00 



Peroxide of iron, ........ 1-65 



Alumina, . . . . ... . . . 1-22 



Carbonate of lime, ........ -10 



Phosphate of lime not appreciable, ...... -00 



Carbonate of magnesia, . . . . . . . -01 



Alkalies, not appreciable, . . . . . . . -00 



Inorganic acids and loss, . . . . . . .1-00 



100 00 



