.232 GEOLOGY OP ILLINOIS. 



times found of full thickness, but without a roof, while in others, only a streak 

 of coaly matter is left. 



The extent of the beds of the Coal Measures, below this seam, is unknown. 

 They here rest directly upon the greenish, sandy shales of the Cincinnati 

 group, which, to the uneducated eye, are not readily distinguishable from the 

 bluish drab, sometimes sandy, shales of the Coal Measures. 



Niagara Limestone. No Sub-carboniferous or Devonian beds are known to 

 exist in Kankakee county. It is, of course, possible, that such may remain 

 in place, under the high country of the southeastern corner of the county, but 

 their existence is in no way indicated, and is altogether improbable. 



The highest Silurian beds exposed are impure earthy limestones which out- 

 crop along the Iroquois, from Sugar Island, at the county line, nearly to its 

 junction with the Kankakee. The outcrop covers so much space that it would 

 be difficult to make any exact measurement of the thickness of these irregu- 

 larly bedded strata. I estimated them at from fifty to sixty feet. They have 

 mostly a moderate dip to the southward. Some of the layers have been quar- 

 ried, in the small way, for local use ; and many of them appear well fitted for 

 making hydraulic lime. 



These beds apparently correspond in position with the Leclaire limestones, 

 forming the top of the Niagara group ; there is no marked separation from the 

 lower beds. A few indistinct plant markings were the only fossils found. 



Apparently belonging between these beds and those which outcrop near the 

 mouth of the Iroquois, though on that stream no equivalent strata were seen, 

 are the layers which are quarried at Momence. Here, we find from fifteen to 

 eighteen feet of light gray and drab, impure, argillaceous limestone, the upper 

 half of which contains great numbers of concretions of chert and silicified 

 corals ; but the lower half makes a fine building and monumental stone, and is 

 largely quarried in the bed of the river. There are also exposed, just above 

 town, a few feet of light buff, very vesicular, magnesian limestone, full of casts 

 of fossils, which is burned for lime. This apparently belongs beneath the 

 quarry-stone. Among the fossils of this bed were observed Pentamerus, 

 Knightii, Bumastes, Platyostoma, Favosites, Cystiphyllum, and fragments of 

 undetermined crinoids. 



Along the river, between Momence and Aroma, a small amount of thin- 

 bedded limestone crops oufr, but presents no opportunity for measurement. 

 Both at Aroma, and for a short distance up the Iroquois, we find from ten to 

 twenty feet of thin, roughly-bedded, pretty compact, light drab and buff lime- 

 stone, occasionally cherty, and full of the striated marks of pressure and slip- 

 ping, which are called stylolites. These are locally used for building, though 

 not at all a handsome material. !No fossils were obtained here, though they 

 probably occur. 



