116 GEOLOGY OF ILLINOIS. 



stone. This bed is overlaid by about nine feet, in vertical thickness, of a 

 thin bedded, yellowish, or dark buff limestone, showing a light gray color, 

 on freshly fractured surfaces, and closely resembling the upper portion of the 

 rock at Torode's quarry, on Salt creek. The upper beds in these quar- 

 ries afforded specimens of Atrypa reticularis, Strophomena rhomboidalis, Or- 

 this flabellum, Leptsena transversalis, Spirifera radiata, S. Niagarensis, Or- 

 thoceras undulatum, Calymene BlumenbacMi, and species of Illsenus and Sphae- 

 rexochus, together with many corals and bryozoa. The lower beds were alto- 

 gether less abundant in individuals j the species were mainly the same. In 

 many cases, the fossils were merely casts, but some were nearly perfect. 



Going from Naperville, in a southeasterly direction along the western bank 

 of the creek, we find, at a distance from the town of a mile or a mile and a 

 half, limestone, apparently the same as the upper beds at Naperville, occurring 

 in the bottom of ditches and small runs, and alongside of the road. Still far- 

 ther on, at Kimball's mill, a thickness of eight or nine feet, probably of the 

 lower bed, is shown at the western end of the milldam, on the right bank of 

 the stream. On the opposite bank, about two hundred yards above the dam, 

 on the southeastern quarter of section 19, township 38, range 8, the upper beds 

 are well exposed, and have been quarried. Here, they yield in abundance, 

 the same species of fossils as at Naperville, and in the same condition. Below 

 Kimball's mill, the lower beds of buff limestone appear along the western bank 

 of the creek for a short distance, and have been quarried at one or two points. 

 It disappears entirely, however, under the Drift, before reaching the county 

 line. 



In Kane county, all of the exposures of rock, with one exception only, are 

 along Fox river. Along this line of outcrop, the greatest development of the 

 formation is at Aurora and Batavia, and between these two points. Both above 

 and below this particular portion of the river, a lesser thickness of the forma- 

 tion is exposed. Commencing at the southern limit of the county, and going 

 up the river, the following are the principal exposures met with : 



At the village of Montgomery, and almost exactly on the southern line of the 

 county, there is an exposure of about eight or nine feet of thin bedded buff lime- 

 stone, abounding in thin seams and flattened nodules of chert, which appears 

 much broken up and decomposed on the exposed surfaces. No good speci- 

 mens of fossils were obtained at this point, and only a few unrecognizable frag- 

 ments were observed. On the opposite side of the river, at the eastern ex- 

 tremity of the milldam, rock was again observed, similar in lithological char- 

 acter to that at the first mentioned outcrop, only that it was harder, less de- 

 composed, and more free from chert. A slight dip, one or two degrees, to the 

 northeast or a little more north, was observed at these exposures, which would 

 apparently bring the one last described above the other. The whole thickness, 



