Pleistocene Deposits of Illinois. — Hershey. 
289 
buried under glacial deposits, but the existence of which the 
eroded bank of the creek reveals just east of the ravine. 
Thence it was pushed forward and deposited in hollows of the 
surface of a previous lacustrine deposit. It contains no glacial 
nor foreign pebbles, but its structure indicates a crushing and 
movement by the ice. This, together with similar deposits in 
all portions of the district, seems to me to indicate that the 
Kansan ice-sheet, which deposited the boulder-clay of north¬ 
western Illinois, was the first to reach the vicinity of Freeport, 
and when it did so found an undisturbed preglacial soil in 
possession of the surface. (In passing, I may remark that, 
among all the exposures of pre-Kansan soil examined by me, 
no instance has been observed of the preservation of any 
black carbonaceous surface soil; and it is presumed that none 
existed, but that the red clay as now seen, although evidently 
chiefly a subsoil, also extended nearly or quite to the surface, 
indicating undoubtedly a warm climate, since red soils are 
characteristic of the southern states and of tropical lands and 
are evidently related to their climatic conditions. The 
Aftonian soil was red also to a certain extent.) 
Before proceeding to a discussion of No. 5, I wish to des¬ 
cribe another section, situated in a cutting of the Illinois 
Central railroad two and a half miles southeast of Freeport. 
The surface deposit consists of from 3 to 5 feet of light brown 
loam of Upland Loess, with the usual black soil at the surface. 
Below this there are about 8 feet of the boulder-clay series, 
divided into 5 feet of yellow till, overlain by about 3 feet of 
the reddish brown modified till constituting the Aftonian 
interglacial soil. Canadian pebbles abound and striated stones 
are frequently found in the lower portion of the series. The 
western end of the cutting shows heavy deposits of water- 
worn gravel, sand, and boulders, of the esker series, resting 
partly on the rock and partly on the laminated clays which I 
am about to describe. These occur directly under the boulder- 
clay, and are not separated from it by any erosion interval or 
other hiatus; the formation of one followed immediately on 
the formation of the other. The laminated clays in this type 
section have an exposed thickness of 15 feet. Their compo¬ 
sition is essentially that of the boulder-clay. But there has 
been a slight sorting of materials by the action of currents in 
