272 GEOLOGY OF ILLINOIS. 



CHAMPAIGN AND FORD COUNTIES. 



These counties occupy a nearly central position in the State, measuring north 

 and south, and lie in the second tier of counties from the Indiana line. They 

 are near the center of the Grand Prairie, and have an almost exclusively prai- 

 rie surface. The groves are few and small, and are situated upon the small 

 streams which head in these counties. 



Champaign county contains about ten hundred and eight square miles, being 

 about thirty-six miles from north to south, and about twenty-seven from east 

 to west. 



Ford county consists of two parts, the one adjoining Champaign county, 

 about fifteen miles from north to south, and twenty-seven miles from east to 

 west ; the other, running thirty miles northward, between Iroquois and Liv- 

 ingston counties, to the south line of Kankakee county, with a width of only 

 six miles. 



So far as is known, there is no outcrop of rock within the limits of these 

 counties. Scattered over their area, there are many large drifted masses of 

 Niagara group limestone, and Coal Measure limestone, and sandstone. These 

 are, in some cases, of very large dimensions, and have yielded considerable 

 quantities of stone for local use ; so that some persons have supposed them to 

 be solid beds of rock. The evidence is, however, as we have stated, that no 

 solid bed reaches the surface. 



The soil is mainly the rich black prairie muck, from one to five feet thick, 

 underlaid, in most cases, by a yellow clay subsoil. Along the sloughs and 

 ponds, the subsoil is a tough brown to yellow clay, with numerous small fresh 

 water shells of the genera Physa, Limnea, Plcmorbis, Ct/clas, etc. These are 

 often so numerous as to give a whitish cast to the whole mass. We have not 

 heard of the finding of any Mastodon remains in these beds, though they are 

 not rare in similar situations in adjoining counties. 



The subsoil is underlaid by irregular alternating beds of clay, gravel and 

 quicksand of the Drift formation, to the depth of from one hundred and fifty 

 to probably three hundred feet. 



In an attempt to sink a coal shaft at Champaign, Mr. John Faulds found 

 the following section : 



FEET. 



Soil, clay and quicksand 17 



Red and blue clay 73 



Peat 2 



Quicksand, containing a tree seven inches in diameter. . . ', 9 



