226 THE POPULAR SCIENCE MONTHLY. 



fifteen miles, appears to have been under the lake waters during 

 the greater time of the westward overflow. Its level surface, its 

 fine, dark soil, and the occasional sandy ridges that traverse it 

 have already been mentioned. Its western boundary, at the point 

 where the Rock Island Railroad gradually ascends to higher 

 ground, is rather distinctly defined by a low but definite bank, 

 apparently an old shore line of the lake, the base being near the 

 contour of six hundred and twenty feet. 



Farther west there is a belt of higher ground, whose contours 

 reach seven hundred or seven hundred and fifty feet. On the topo- 

 graphic maps this belt appears to be a plateau-like swell, well dis- 

 sected by streams ; but on the ground it has the appearance of a 

 faintly marked moraine, and it is so represented on the soil map 

 of Illinois, prepared by Mr. F. Leverett and exhibited in the Illi- 

 nois State Building in the World's Fair. Its morainic form is 

 indicated by numerous faint mounds and small hollows, and the 

 railroad cuts show it to be composed largely of drift. The spurs 

 and valleys, apparently of simple drainage development as indi- 

 cated on the map, do not justly represent the expression of the 

 surface at this point. A more appreciative drawing of the contour 

 lines is required to express this faint morainic topography ; but I 

 do not think it should escape representation on a scale of 1 : 02,500. 

 It would be interesting to compare a careful contouring of a small 

 portion of this belt with its generalized portrayal on the survey 

 sheets. 



The old channel, now occupied by the Desplaines, crosses this 

 belt of higher ground in a well-marked trough. The breadth of 

 the flat bottom of the trough is almost constant at a measure of a 

 mile ; its depth below the immediately adjacent upland is about 

 seventy-five feet. This is partly cut in horizontal Niagara lime- 

 stone, and the descent into the flat-bottomed trough is accom- 

 plished on steep sloping bluffs, somewhat dissected by narrow, 

 short, and steep-sided ravines. This may be called the Lemont 

 channel, from the village of that name at its middle, where quar- 

 rying is now going on in the limestone in order to increase the 

 westward discharge from Lake Michigan, as stated above. 



The morainic belt has a width of fifteen or twenty miles on 

 the Desplaines and Joliet sheets. Joliet lies near its western base. 

 Farther west there is a second belt of higher country, also repre- 

 sented as a morainic belt on Leverett's map, of which further 

 mention will be made below. Between the two belts there is a 

 strip of lower country, about twenty-five miles wide, whose eleva- 

 tion at and below the junction of the Desplaines and Kankakee 

 Rivers varies from six hundred to five hundred and fifty or less. 

 This I shall call the Morris basin, from a town of that name near 

 its middle. On entering the basin, the old channel is less dis- 



