THE LAKE-BOEDER MORAINIC SYSTEM. 403 



At Fennville wells in some cases penetrate 50 feet of sand, with which 

 there are thin beds of peaty material associated. A hill east of this village, 

 which stands about 50 feet above the level of the railway station, has till at 

 the surface. 



At Drenthe, on the inner slope of Covert Ridge, in southern Ottawa 

 County, flowing- wells have been obtained; one in a ravine at the sawmill 

 has a head 8 feet above the surface and will flow SO barrels per day from 

 a 2-inch pipe. The water is obtained from sand below blue till at a depth 

 of 92 feet. Another well a few rods Avest is siphoned into a trough in 

 the same ravine. A well 1 mile north of Drenthe, 155 feet in depth', is 

 mainly through blue till, exce]3t in the lower 15 feet, where water-bearing 

 sand and gravel is found. Its head is sufficient to barely reach the surface. 

 Many wells along the ridge east and south from Drenthe have been sunk 

 to a depth of 100 feet or more, mainly through blue till. The till sheet 

 extends westward from this ridge to the shore of Lake Michigan in north- 

 western Allegan County. 



CHARACTER OP THE OUTWASH. 



The Valparaiso morainic system formed a retaining wall for waters 

 escaping from the ice sheet along the outer border of the ridges under dis- 

 cussion, except at the "Chicago Outlet," and possibly at the St. Joseph 

 River Valley. It is probable therefore that the district between the ice 

 margin and the Valparaiso morainic system was occupied either bv lakes 

 or by very sluggish streams, except perhaps for a few miles in Lake and 

 northern Cook counties, Illinois. There are found indications of a moderate 

 rate of flow, accompanied by gravelly outwash, along the Des Plaines 

 Valley below the point where the outer ridge crosses the river near Grurnee. 

 The force of the current was sufficient to carry the gravel as far down the 

 valley as the vicinity of Des Plaines Village and form a belt a mile or more 

 in average width. The gravel is only a few feet in depth. 



Much of the low country bordering these ridges in southern ('(ink 

 County, Illinois, and in northwestern Indiana and southwestern Michigan 

 has been covered by the waters of Lake Chicago, and the deposits made by 

 ' this lake can not easily be separated from any deposits of similar character 

 which may have been formed as an outwash from the ice sheet. There are 



