62 Geology of ike Monongahela Valley, 



It contains some fossil marine shells, chiefly Encrini, and other or- 

 ganic remains. This deposit is very extensive and is found on, or 

 near the tops of the mountains, for nearly the whole length of the 

 ranges. — 300 feet. 



2. A thin deposit of coal, with shale, about 3 feet. 



3. Limestone, in a deposit of great extent, being found under 

 the coarse conglomerate through the whole of this range of moun- 

 tains. Its structure is not so compact as that of the limestone on 

 the Shenandoah river, and generally of that S. E. of the mountains, 

 but it is fragile, and broken into fragments of all sizes, as it lies 

 in its bed. It contains fossil shells, and especially madrepores and 

 corralines. Figure No. 25, (page 14 of the wood cuts,) is from 

 this bed ; No. 26, (Id.) is from the vicinity. In the County of 

 Pocahontas, on the heads of Greenbrier and Gauly rivers, the 

 limestone is very full of them, and as its cohesion is slight, it easily 

 crumbles on exposure to the weather, and the madrepores are thus 

 loosened, and falling out, remain on the surface in great numbers. 

 They are generally replaced by silex. This bed is seventy five feet 

 in thickness. 



4. A deposit of slate or shale, containing impressions of ferns, 

 and arundinaceous plants. It is only a few feet in thickness. 



5. Sandstone, of various qualities, from coarse pebbly conglom- 

 erate to very fine argillaceous, in beds of various thickness, from a 

 few feet to several hundred. Some beds contain mica. This for- 

 mation continues to the Valley river at the foot of the mountains, 

 fifteen hundred feet in thickness. In the heads of the valley, which 

 is itself more than twelve hundred feet above tide water, we find 

 limestone and coal. The coal is in thin beds, and of a poor quali- 

 ty. It may be received as a general law applicable to the coal in 

 the valley of the Ohio, that the thicker the deposit, the better the 

 quality of the coal. South of Clarksburgh, the coal diminishes rap- 

 idly, both in quantity and in excellence. In the vicinity of this 

 town, and north of it, down the valley of the Monongahela, we find 

 one of the richest and most abundant deposits of coal, in all the val- 

 ley of the Ohio. The beds seem to have been deposited in a ba- 

 sin, the centre of which is now occupied by the bed of the river. 

 I am led to this conclusion, from the fact of the thickest beds being 

 found near the river, and from their becoming thinner as we travel 

 east or west of this line. Two or three of the surface deposits, are from 

 six to ten feet in thickness, and one near Clarksburgh, one hundred 



