GEOGRAPHICAL CHANGES DURING PENNSYLVANIAN 159 



wickley, not pebbly at the northwest, but coarse and often pebbly in 

 southern Ohio. In Pennsylvania and northern Ohio a more or less per- 

 sistent sandstone, the Uniontown, overlies the Uniontown coal bed, but 

 ordinarily it is unimportant and many sections show little aside from 

 shale in the interval. In West Virginia, however, a strip of coarse con- 

 glomerate, evidently at this horizon, crosses the state from east to west, 

 passing through Lewis, Gilmer, Doddridge, Tyler, and Pleasants counties 

 and extending into "Washington, Morgan, and Athens of Ohio, where it is 

 the 200-foot conglomerate of Professor Andrews. It is coarser in "West 

 "Virginia than in Ohio. The strip is very narrow in the former state and 

 fine-grained rocks replace the coarse material at a short distance north 

 and south ; but in Ohio the area is broader, as though additional material 

 had been brought in from that side. This east-and-west line of coarse 

 rock recalls those of the Beaver and Conemaugh in Pennsylvania and 

 may be explained in the same way. The general distribution of coarse 

 material indicates a rising border land and for the southwest a notable 

 encroachment. 



The limestone deposits of the Monongahela deserve more careful con- 

 sideration than can be given here, under the limitations set for this 

 description. These rocks vary greatly in composition. The Eedstone 

 is an impure limestone, yielding a fair lime when burned carefully; the 

 Fishpot, when thin, usually resembles the Eedstone, but when thick it 

 is apt to contain some layers of cement rock; the Benwood has several 

 beds of hydraulic limestone, even of cement rock, among its most per- 

 sistent members, while some of the beds are so impure as to break into 

 small angular fragments after continued exposure; the "Uniontown and 

 "Wajraesburg are rarely more than slightly magnesian. 



Of the numerous limestones, only the "Uniontown can be regarded as 

 really persistent; it is present in western Pennsylvania and in Ohio at 

 nearly every locality where its place is shown. The others may be re- 

 garded as confined to southwest Pennsylvania, the "West Virginia pan- 

 handle, and the immediately adjacent part of Ohio. Their great develop- 

 ment is between the Monongahela river at the east and the Ohio river 

 at the west, where in considerable areas limestone and calcarous shale 

 fill more than one-half of the interval between the Eedstone and Union- 

 town coal beds. In all directions from this small area the limestone 

 diminishes quickly and is replaced by shale and sandstone; toward the 

 southwest only some thin streaks remain in "West Virginia, and in some 

 portions of that state those streaks seem to be replaced by red shale. 



These limestones are spoken of commonly as merely calcareous muds, 

 and that explanation of their origin was accepted tentatively on a pre- 



