72 LOWER PENINSULA. 



slabs of chocolate-brown color ; below them is usually found a 

 band of conglomerate not over a foot in thickness, composed of 

 pebbles of sizes ranging from that of a pea to that of a hazle- 

 nut. Then comes a fine-grained, micaceous, greenish-colored sand 

 rock, and a few feet below the upper conglomerate another seam of 

 it often follows ; but these conglomerate bands are not regular ; they 

 ■vvedge out on both sides, while, in places, no such seam is developed. 

 The conglomerates contain a large proportion of calcareous cement, 

 and are usually very hard. The sand-rock beds between the con- 

 glomerates often contain single pebbles scattered through them, and 

 globular concretions from the size of an Qgg to that of a man's fist, 

 of extremely hard, calcareous sand-rock mass, which, split open, 

 are nearly always found to inclose some kind of a fossil, bones 

 of fish, or Goniatites, etc. ; the same fossils are found in the 

 conglomerate seams. The sand-rock ledges inferior to the con- 

 glomerates represent the useful quarry rock, having a total thick- 

 ness of about i6 feet. It is a middling, fine-grained sandstone, 

 micaceous, of bluish or greenish color, in places very regularly strat- 

 ified, and all through homogeneous, splitting in even beds, with 

 sometimes ripple-marked surface. In some parts of the quarries, 

 however, the bedding is discordant, as it is found in every sand- 

 stone formation, involving a greater proportion of waste. Some- 

 times also layers are damaged by single quartz pebbles scat- 

 tered through them, which unfit them for use as grindstones. 

 The rock is split into plates of any desirable thickness, dressed 

 roughly with the hammer, and is then finished by a steam-turning 

 niachine ; portions also are sawed into strips for use as whetstones. 

 Grindstones of 6 and 7 feet in diameter can be easily obtained. 

 The blocks not well suited for grindstones are either dressed on 

 the spot as building material, or are shipped in the rough, to be 

 used for the same purpose. 



I have already mentioned the occurrence of Goniatites and Fish 

 remains in the conglomerate beds and in the calcareous concretions ; 

 the same fossils, although more rarely, are also found in the other 

 parts of the rock series. Teeth and spines of various fishes of 

 the shark family are found in great perfection ; among these I may 

 mention a tooth of an Orodus 4|- inches long. This specimen, 

 besides a number of others, I gave into the hands of Prof. New- 

 berry for description, the study of fossil fishes being a specialty 



