GRUNDY COUNTY. 



township. The rock here is a rather more solid limestone, breaking irregu- 

 larly, and containing but few fossils. It is reported that similar small outcrops 

 occur farther up this run, but they have not been opened, so as to know whether 

 stone of any value can be obtained. Similar outcrops were observed in the 

 bottoms of ditches near the middle of the north line of township 34 northj 

 range 7 east. In the borings about Morris, only a few feet of beds which can 

 be referred to this group are found between the Coal Measures and the under- 

 lying Trenton limestone, and to the northward of that place, no such beds have 

 been found. 



Trenton Limestone. The two remaining outcrops of rock in this county are 

 limestones of the Trenton group, probably near its top. The principal one is 

 near the center of section 24, township 34 north, range 7 east, where Mr. H. 

 Waters has, for "some years, quarried stone for building and for making lime. 

 The top layers of the quarry are thin, and somewhat stained with iron. Be- 

 low these, the rock is a heavily bedded, gray or light drab, fine grained, clink- 

 ing limestone, not very rich in fossil, but yielding some good specimens of Re- 

 ceptac^llites, Illsenus, Strophomena, Leptsena, Orthis, Discina, Murchisonia, Or- 

 thoceras, etc. These have been penetrated to the depth of twenty feet, without 

 exposing any other layers ; but it is said that at one point the drill passed 

 into a pocket of a softer black material, which strengthened the owner's pre- 

 vious opinion that the coal seam extended under his quarry. Possibly this 

 may have been a small deposit of carbonaceous material analagous to the petro- 

 leum which this rock has yielded in small quantities in the adjoining county of 

 LaSalle. These beds contain small portions of pyrite (sulphid of iron) dis 

 seminated through the whole mass. There were also occasional streaks of soft 

 clay. The quarry has exposed two sets of crevices, one tending south 45 

 west, and the other south 35 east. These crevices are filled with a fine clay 

 of very nearly the same color as the limestone, through which are sparsely dis- 

 seminated small crystals of blende (sulphid of zinc,) with occasional pyramidal 

 crystals of pyrite ; no galenite has been observed. 



The remaining outcrops of this rock are in the beds of the AuSable, on the 

 two sides of the yoke-like bend of the stream, in the east half of the northeast 

 quarter of section 19, town 34 north, range 8 east, and consist of small patches 

 of a thin-bedded, fine-grained limestone, containing but few fossils. 



In the Morris boring, the Trenton limestone is two hundred feet thick. 



St. Peters /Sandstone. This rock has been struck at the railroad station in 

 Morrs, at a depth of about three hundred and seventy feet, and here, as else- 

 where in this region, has furnished a constant and abundant supply of artesian 

 water. 



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