48 Introduction 



differed so strikingly from the generally accepted correlation and struct- 

 ure of this region that the following spring Dr. I. C. White reexamined 

 the Potomac River section from Piedmont to the summit of Knobly 

 Mountain on the West Virginia side of the river to the east of Keyset. Dr. 

 White's paper is a valuable addition to the knowledge of the structural 

 and stratigraphical geolog}^ of western Allegany County and shows con- 

 clusively that the quartzose sandstone capping Wills Mountain, which Mr. 

 Jones called the Pocono, is the White Medina (Tuscarora), while the red 

 beds below instead of representing No. IX (Catskill) as Mr. Jones 

 supposed, are the Ked Medina (Juniata). The 440 feet called the Lower 

 Mountain Limestone by Jones, is identified by White as the Lower Helder- 

 berg and the lower 2000 feet of red shale on the Potomac which Jones sup- 

 posed to be a repetition by folding of No. XI (Mauch Chunk) is correctly 

 referred by White to the Catskill (Hampshire). 



The geology of Bedford and Fulton counties, Pennsylvania, bordering 

 those of Paleozoic Maryland, was published in 1883 by Prof. John J. 

 Stevenson who fully adopted the New York classification and whose 

 accurate correlation has given this work a permanent value. 



Professor Wm. B. Rogers prepared the list of geological formations 

 found in Virginia and West Virginia for the first edition of MacFarlaiie's 

 Railway Guide published in 1879, in which he gave the New York names 

 first place, while in two parallel columns are given the equivalents in the 

 Roman numbers of the Pennsylvania and Virginia annual reports and the 

 names of the Pennsylvania final report. The same scheme of classifica- 

 tion was used in explaining the colors on " Hotchkiss' Geological Map of 

 Virginia and West Virginia." The geology by Prof. W. B. Rogers, pub- 

 lished in 1884, is a reproduction, with some changes, of the one published 

 in 1876. The Devonian is given as composed simply of Nos. VIII and IX 

 and is represented by a single color. 



In the second edition of MacFarlane's Railway Guide, published in 

 1890, I. C. White prepared the " Table of geological fonnations in West 

 Virginia" (p. 337) in which he fully adopted the New York names, 

 although the Pennsyhaiiia numbers are given in another column, but the 

 names of Rogers' final report are not mentioned. 



