DEKALB, KANE AND DUPAGE COUNTIES. 115 



In the eastern portion of DuPage county, on the northwestern quarter of 

 section 2, township 39, range 11, about half a mile west of the railway station 

 at Cottage Hill, a light gray or nearly white sub-crystalline limestone is quar- 

 ried. The rock is concretionary in its structure, showing bedding very imper- 

 fectly, and though very full of traces of organisms, affords but very few well 

 preserved fossils. The whole depth of the quarry is fifteen or twenty feet, but 

 at the time of my visit only about ten feet of the upper portion was exposed 

 the bottom of the quarry being filled with water. Directly east of this point, 

 in the village of Cottage Hill, rock is said to have been struck in a well at a 

 depth of twelve feet. The rock exposed in this quarry is not seen in any of 

 the other outcrops in this district so as to be identified by its lithological char- 

 acters. It seems possible, indeed, that this may be the uppermost bed of the 

 Niagara group within these limits. 



Passing to the southward about three miles, we find the nearest outcrop oc- 

 curring on the western bank of Salt creek, in the southwestern quarter of sec- 

 tion 14, on the land of Mr: Torode. About nine feet in thickness of thin bed- 

 ded limestone is here exposed, the upper two or three feet, porous and yellow, 

 the remainder, a rather even textured stone, light drab or gray in color, and 

 containing numerous nodules of chert. The beds appear to increase in thick- 

 ness, the deeper the rock is- worked. There is in this quarry a slight, in some 

 places almost imperceptible, local dip to the northward. The upper portion of 

 the rock exposed at this place, is fossiliferous, affording various corals, crinoids, 

 bryozoa, and brachiopoda, but generally ill preserved, and often indistinguish- 

 able as to species. 



Further to the southward, no exposures are met with, until the vicinity of 

 the DesPlaines river is reached, where we find the bottom land opposite Le- 

 mont, underlaid by limestone beds. The rock also appears to a limited extent, 

 near the base of the bluffs, on the northwestern edge of the river bottom, but 

 no good exposures are met with on this side of the river. On the flats, it is 

 generally covered with a thin layer of surface soil, and wherever it does appear 

 at the surface, is so changed by weathering as to make an almost complete 

 alteration in its appearance. It seems probable, however, the beds at a suffi- 

 cient depth under the surface, may afford a good building material. 



To the northwestward of this, the only remaining outcrops of rock in DuPage 

 county, are met with on the western fork of the DuPage river, at Naperville 

 and below. At Naperville, in the quarries on the southwestern bank of the 

 creek, just below the milldam, there is a section, consisting at the base, of an 

 even textured, regularly bedded, light drab or buff limestone, about six feet of 

 which is exposed in the excavation. Nodules of chert, of irregular flattened 

 forms, are quite frequent in the upper part of this bed, but less abundant be- 

 low, where the layers also appear to be thicker and more adapted for a building 



