120 REPORT OF THE 



must be very limited, so that in general terms, the whole area 

 will be found productive. 



From the numerous sections which have been given, it ap- 

 pears that one persistent seam of coal runs through the whole 

 formation. This ranges in thickness between three and five 

 feet, being thinnest near the borders of the b^asin. Toward the 

 central axis of the basin, all the members of the series thicken, 

 and several accessory seams of coal make their appearance. 

 When this occurs, one of the seams is a cannel coal about 2 

 ft. in thickness. Immediately above this seam is a belt of 

 black band, becoming in places highly calcareous, and passing 

 into a black ornamental limestone or marble. To present the 

 general structure of our coal measures more clearly to the mind, 

 we may make use of the following table: 



E. Bituminous shales and light clays, 40 ft 



D. Black hand passing into black limestone, 2 ft 



C. Bituminous and Cannel Coal in one or more seams, with 



aggregate thickness of 3 to 11 feet, 1 1 ft. 



B. Fire-clays and sandstones, 23 ft 



A. Shale, clay, sandstone and thin seams of coal, 50 ft. 



The shales of the coal measures are well stocked with tho 

 remains of the terrestrial vegetation. Fern leaves, in a beauti- 

 ful state of preservation, are sometimes found in the black band. 

 But few marine fossils occur, and these have been already 

 noted. 



17. — Woodville Sandstone. 



Some account of this formation has necessarily been embraced 

 in the description already given of the Coal Measures, and I 

 shall add but few observations. Wherever it is not denuded, 

 it is the capping stone of the coal measures. It is a friable, 

 rather coarse, quarlzose sandstone, stained to a variable extent 

 with oxyd of iron. At Jackson, the rock is nearly white, and 

 has been used in the manufacture of fine glass; at Corunna it 

 is pale buff, and embraces abundant rich nodules of kidney iron 

 ore, which, on the disintegration o#the rock, are left in the soil; 

 at Ovvosso it is flesh colored; near Lyons, in Ionia county, it is 



