596 THE GEOLOGY OF MINNESOTA. 



[Soil and timber. 



Nearly the whole of this district is prairie, or natural grass-land without trees or bushes. 

 Excepting a tenth or twentieth part, occupied by sloughs, this is dry, undulating or rolling up- 

 land, which affords excellent pasturage, but yields less than half as much hay per acre as the 

 wet lowlands. Its smooth areas are ready for plowing and sowing, and are mostly occupied by 

 farms, though as yet only a small part of the land has been brought under cultivation. Its yearly 

 product of wheat to the acre is ten to twenty-five bushels. Many other crops grow well, includ- 

 ing oats, corn, barley, potatoes, and the common garden vegetables and small fruits. 



The agricultural value of the belts occupied by the terminal moraines, with their small and 

 steep knolls and ridges, and abundant boulders, is much less than that of the smooth drift which 

 covers the other parts of this region. Among the hills of this formation, however, are found con- 

 siderable areas which have a smooth surface, nearly free from boulders, and possess a rich soil; 

 while the portions which are too knolly and stony for desirable cultivation are valuable for graz- 

 ing. 



Timber occurs in this district only in narrow belts along the rivers and in groves of small 

 area bordering lakes. At the northeast side of Yellow Medicine county, it fringes the bank of 

 the Minnesota river, but leaves much of the bottomland treeless, excepting an extent of about 

 three miles, lying below (southwest and south from) Minnesota Falls, where the entire side of 

 the valley west of the river, a quarter to a half mile wide, is occupied by a stately forest of bass, 

 elm, bur oak, white ash, box-elder and other species. The bluffs of this part of the valley have 

 frequent groves, especially in ravines, but their only portion continuously and fully wooded is in 

 the tract just mentioned, within a few miles below Minnesota Falls. 



Wood lake and the lake of the Woods, in the southeast part of Yellow Medicine county, 

 derive their names from the small patches of timber that skirt their shores. The priLcipal spe- 

 cies of trees found at Wood lake, in their estimated order of abundance are white elm, white ash, 

 red or slippery elm, box-elder, bass, bur oak, haekberry, wild plum, willows and cottonwood. 

 The lowest ten or fifteen miles of the valley of Yellow Medicine river have considerable wood- 

 land, and bushes and small trees border its banks along much of its upper portion; but the 

 greater part of this stream and of the Lac qui Parle, Redwood and Cottonwood rivers, from the 

 foot of the Coteau des Prairies to the border of this district, are destitute of timber or only scan- 

 tily wooded. On the northeastern slope of the Coteau, the ravines of the creeks which form the 

 head-waters of these rivers contain many groves and narrow belts of timber, the largest amount 

 being in the deeply excavated valley of the Redwood river in Lynd. Farther westward most of 

 the lakes upon the Coteau are fringed with wood on some part of their shores, but there are no 

 notably large tracts of timber in this part of the district. At the Coteau lakes, near the crest of 

 this highland, in central Deuel county, Dakota, thirteen miles west of the state line, a tract of 

 woods about a mile long and a third of a mile wide, almost enclosed by a group of four lakes, has 

 the following species of trees and shrubs, according to Mr. J. C. Godard, who lives there: bur 

 oak, white ash, white elm, box-elder, wild plum, willows, Virginia creeper, climbing bitter- 

 sweet, frost grape, smooth sumach, black and red raspberry, choke-cherry, thorn, rose, black cur- 

 rant, red elder, prickly and smooth wild gooseberries, and waahoo, common; and cottonwood, 

 haekberry, black cherry, wild red cherry and sheep-berry, less common. 



GEOLOGICAL STRUCTURE. 



Eozoic rocks. A broad belt of granite, syenite, gneiss, and related crys- 

 talline schists, of Eozoic or Archaean age, extends from northeastern Min- 

 nesota southwesterly to the Minnesota river. Its outcrops in this district 

 are confined to Yellow Medicine county, within the deeply eroded Minne- 

 sota valley, and at three localities from ten to twenty miles farther south- 

 west, lying in Echo, Posen and Omro townships. 



At Granite Falls and Minnesota Falls ledges of gneiss rise on both sides of the river, filling 

 the valley with a multitude of knobs and short ridges, 30 to 75 feet high. These rocks begin five 



