Mesozoic and Cmnozoic Geology and Palceontology. 331 



follows along the eastern Hue of that count}^ passes into Portage, 

 curves westward, and crossing the Wisconsin river again, continues in 

 a nearly westward direction across Wood, Clark, Jackson, Trempea- 

 leau, and Buffalo counties, to about the foot of Lake Pepin, on the 

 Mississippi. 



He says, that east of this limit, the fragile castellated outliers that 

 abound in the driftless area are wanting, though outliers do occur, 

 though not abundantl}', and t\\Qy are thick and of rounded contour, 

 and more commonly of limestone; but that north of this line the drift 

 is quite insignificant, and all surface irregularities are as purely the 

 result of subperial agencies as in the driftless region itself. And this 

 corresponds with the outliers in Dakota county, Minnesota, mentioned 

 above, which are north of Lake Pepin, and within the drift area. 



There are several grand outliers in Jackson county, Illinois; one of 

 these is called the " Back-bone," and another the " Bake-oven." The 

 uplands contain some drift and gravel, but none have been observed 

 south of the dividing ridge that crosses the State through the south 

 part of this county and the north part of Union. The drift clays and 

 gravel do not average more than 20 feet in thickness, and below these 

 there is frequently found a dark blue or black mud, containing branches 

 of trees, and sometimes trees of large size. In Perry county, the drift 

 deposits seldom attain a thickness of more than 30 or 40 feet. But 

 below them, as in Jackson county, there is a laj^er of blue mud lying 

 on the stratified rocks, which is so full of partly decomposed vegetable 

 matter, consisting of leaves and wood, as to render the water in wells 

 that penetrate it, unfit for use. In Jerse}^ county, the drift consists of 

 about 20 feet of yellowish-brown clay at the top, below which there 

 occurs from 20 to 30 feet of sand and gravel, with bowlders; and this 

 is underlaid by about 15 feet of blue plastic clay, which contains frag- 

 ments of wood, and even trees of considerable size. In Greene, Cal- 

 houn, and Scott counties, there is some evidence of buried channels 

 where the drift is 100 feet or more in thickness. In Cook count}^, 

 there is abundant evidence of the lake having been 40 feet higher 

 than it is now, and that trees grew upon the surface, at levels lower 

 than the present height of the lake. There is also sorhe evidence 

 here of a buried river channel. In Adams county, below 90 feet of 

 drift clay, with gravel and bowlders, there occur an ancient soil and 

 subordinate clays, without bowlders, or other evidences of drift action. 

 At S3'camore, in DeKalb county, large pieces of wood were met with in 

 the blue clays, at the base of the drift, at 50 feet in depth; and similar 



