Mesozoic and Cenozoic Geology and Paleontology. 227 
follows along the eastern line of that county, 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 outhers do occur, 
though not abundantly, and they 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 subserial 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, [llinois; 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 layer 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 Jersey 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 county, 
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 some 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 Sycamore, 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 
