DEKALB, KANE AND DUPAGE COUNTIES. 119 



quarry, two of these joints, parallel to each other, enclose about ten feet in hor- 

 izontal thickness of the strata, which is said to be shaly and entirely worthless 

 for building purposes, while on either side are continuous strata of valuable 

 stone. Fossils appeared to be exceedingly rare in these beds, and when found, 

 except when in a silicified condition, are very indistinct. 



Just north of the bridge, on the western side of the river, at Batavia, is a 

 quarry, the rock of which is a light yellow limestone, very similar to that at 

 Mill creek, and containing in one of its narrow layers great numbers of Penta- 

 merus oblongus. The whole exposure is of about twelve feet. I consider this 

 exposure, and that at Mill creek, as of a lower bed than those exposed in the 

 six principal quarries at Batavia, which cannot be identified as appearing any 

 more above the surface to the northward of that point. 



From Batavia northward, the ledges may still be observed along the river 

 bank. The rock is probably that of the lower beds, the upper ones may still 

 perhaps be in place higher up in the bluffs, but if so, they are completely cov- 

 ered with soil, and invisible. Before reaching Geneva, however, the ledges 

 disappear and are not again met with until that place is reached. On the east- 

 ern side of the river, a little north of the bridge, a quarry affords a section of 

 about eleven feet, the upper five of which are of a yellowish limestone, similar 

 to that already mentioned as occurring at Batavia and Mill creek. Under this, 

 six feet of a white grayish stone is exposed, which is quarried for building stone. 

 The upper bed affords a few Pentamerus ol>lonc/vs, the lower one appears almost 

 destitute of fossils. A lower bed of similar limestone, exposed on the river 

 bank a little higher up, afforded a few corals and other fossils. 



North of Geneva, the limestone may be observed outcropping at various 

 points, and forming the bed of the river and several smaller streams. The best 

 section which is afforded by any exposure between this point and St. Charles, 

 may be seen at a place called Cedar Bluffs, about a mile south of the latter 

 place. The two lower beds seem similar to those which are exposed further 

 down the river, at Geneva : 



FEET. 



1. A thin-bedded buff and gray limestone, apparently destitute of fossils 7 



2. A bluish or bluish-white shaly bed 1 



3. Brittle yellow limestone, similar to the upper bed at Geneva, and containing many 



Pentamerus oblongus, corals, etc. . , 4 



4. Bluish or grayish-white rock, containing a few fossils, Illcenus, Orthocerai, etc., and 



resembling in appearance the lower bed at Geneva, exposed 3 



Below the lowermost bed in this section, and the level of the river, is a con- 

 siderable thickness of strata, which are not exposed well enough to enable us to 

 judge of their lithological character. Much of it, however, is in all probability 

 the same as No. 4. A half a mile farther north, at McAulay's quarry, the 

 same beds are again seen, but, in this exposure, No. 1 is somewhat thinner, and 



