THE CERRO GORDO MORAINE. 221 



Wisconsin drift has a depth of 150 feet at this point is supported by the fact 

 that the moraine there reaches an altitude nearly 150 feet above the level 

 of the buried soil along the Sangamon Valley at Monticello and near 

 Mahomet. 



Along the ridge from Humboldt eastward into Douglas County wells 

 apparently reach the base of the Wisconsin drift at 65 to 75 feet, and farther 

 east at 50 feet or less. 



The sharp ridge situated in the northeast part of Paris has been opened 

 extensively for gravel. There is at the surface a brownish yellow till 5 

 to 15 feet thick, and beneath this are beds of calcareous sand several feet 

 in depth. Beneath the sand there is a sandy gravel. Both the sand and 

 the gravel show considerable cross-bedded structure.. The beds are also 

 arched, and appear to have been crumpled somewhat as if by a disturb- 

 ance by the ice sheet. In order to ascertain the proportion of the various 

 kinds of rock in this gravel, a small space was marked off in the gravel 

 pit and the pebbles therein were classified, with the following result : 



Classification of pebbles in a gravel pit at Paris, Illinois. 



Granite g 



Other crystalline rocks g 



Quartz 3 



Chert of light color \ 13 



Brown chert 



1 



Carboniferous sandstone (local) XI 



Gray limestone (probably local) ; 45 



Magnesian limestone 4g 



Total li^ 



A few of the gray limestone pebbles are striated. These pebbles show 

 less rounding by water action than other classes. It is probable that some 

 of them are from the Carboniferous limestone exposed near Baldwinsville, 

 north of Paris. 



CHARACTER OP THE OUTWASH. 



The character of the outwash from the Cerro Gordo moraine has 

 received very little attention. It has been noted, however, that the valleys 

 leading away from the moraine, with the exception of the Sangamon, are 

 small and are usually cut in till. There can not, therefore, be very heavy 

 sand or gravel outwash. 



Along the Sangamon River for a few miles below Mahomet this 

 morainic belt is bordered on the west by a gravelly plain, whose origin and 



