132 LOWER PENINSULA. 



nificant intermediate seams of shale, or with an occasional coal seam 

 of a few inches thickness wedged in. Calamites and other vege- 

 table imprints, besides concretions of kidney ore and of iron py- 

 rites and conglomerate seams, are usually found inclosed within 

 the rock mass. In grain and hardness, it fully resembles the upper 

 sandstones of Jackson ; its color, however, is a somewhat darker 

 yellowish shade. Locally the rock becomes very hard and has a 

 dark, chocolate-brown color from containing an abundance of ferrugi- 

 nous cement ; a part of this brown rock is coarsely conglomeratic. 

 Next below this sand rock, which borders the river in vertical cliffs 

 for nearly the length of a mile, we find blue shales of arenaceous 

 character, interlaminated with thin layers of sand rock, all amount- 

 ing to a thickness of about 15 or 20 feet. Under these is a coal 

 seam 2|- feet in thickness, and of very good bituminous quality. 

 It wedges out in places or changes into a black, carbonaceous 

 shale. This seam is worked at times by single workmen, as a tem- 

 porary occupation when they have little else to do. The coal 

 seam rests on a gray, argillaceous, laminated sand rock with 

 softer shaly seams, which both inclose a large quantity of coaly 

 vegetable remains, Lepidodendron, similar to Lepid. Wortheni, 

 Stigmaria ficoides, trunks and leaves. The thickness of the 

 beds is about 5 feet. Lower comes a fine-grained, whitish sand 

 rock in even, compact beds, 8 feet in thickness. Directly under 

 this sand rock is a 15-inch bed of good bituminous coal. Lowest 

 in the outcrop are about 25 feet of additional strata, princi- 

 pally sand-rock ledges, with some intermediate shale seams. In the 

 bed of the river at this spot, large, hard sand-rock slabs, of very even 

 bedding, and from 2 to 3 inches in thickness, are laid open, which 

 would make excellent flagstones for paving sidewalks. The aggre- 

 gate thickness of the given section is about 90 feet ; it begins 

 with the centre of the synclinal depression and is followed down- 

 ward with the stream. Up stream a rise of the strata is seen, 

 but the next lower strata to the upper sand-rock deposit are not 

 uncovered as plainly as at the lower end of the depression. After 

 passing a covered interval of about 60 steps, in going up stream, 

 the following descending section is observed : 



