1881.1 4d9 [White. 



I find no duplication of No. XI, the "2000' red shale," whicli Mr. Jones 

 placed in No. XI, being Catskill, separated from the true No. XI by 1150' 

 of gray Pocono (Vespertine) (X) sandstone; his "440' Lower Mountain 

 Limestone" is Lotcer Helderberg (No. VI); his "100' Pocono sandstone" 

 is the White Medina, more than 10,000' heloic the true Pocono. 



The line of section extends from Piedmont, Mineral county, West Vir- 

 ginia (and Westernport, Maryland, just opposite), south-eastward along 

 the West Virginia side of the North Potomac, to Keyser (formerly New 

 Creek), and one and a half miles beyond to the summit of Knobby moun- 

 tain ("Knobbley"). 



A reference to the accompanying figure will explain the structure of the 

 rocks along the section line which is not far from six and a half miles in 

 length. 



As is well known, the Cumberland, or Potomac Coal Basin, lies in a 

 trough of the Allegheny system with Savage mountain bounding its 

 north-western rim, and Dan's mountain* its south-eastern. The North 

 Potomac, after flowing north-eastward down this great syncline for 

 many miles in West Virginia, receives the Savage river at Blooming- 

 ton, near the Maryland line, whence the combined stream flows east- 

 ward across the Basin to Piedmont, two miles below, and then veering to 

 the south-eastward cuts squarely through the Dan's Front Ridge moun- 

 tain, continuing on across the upturned edges of X, IX, and VIII to 

 Keyser, when trenching through an arch of VII, and the upper portion of 

 VI, across New Creek mountain (ridge), it again flows north-eastward 

 along the north-western slope of Knobby mountain to Cumberland. 



From an inspection of the figure, it will be observed that the strata are 

 almost horizontal in the vicinity of Piedmont, and Westerni)ort ; that in 

 going south-eastward thej" soon begin to rise quite rapidly, the lowest beds 

 of No. XII coming up to the south-east at an angle of 12°, three-fourths 

 of a mile below Piedmont. Nos. XI, X, IX, and VIII come up succes- 

 sively with constantly steepening dips until near the middle of VIII, the 

 rocks are vertical ; finally near Keyser the Oriskany sandstone. No. VII, 

 comes up with a diminished dip, and arching over the anticlinal axis of 

 New Creek mountain, barely dips down to water level on the North 

 Potomac, making a very shallow and sharp syncline, since it immediately 

 returns with a reverse dip of 65° to the North-west, which carries No. VII, 

 VI, and V into the air over the Walker's ridge anticlinal, one-half mile 

 south-east, to come down again on a south-east dip in the monoclinal 

 range of Knobby mountain, whose crest is formed by the Oriskany sand- 

 stone (No. VII), and the underlying cherty layers at the top of the Lower 

 Helderberg (No. VI), the varying composition and unequal hardness of 

 which give rise to the peculiar topography that has given name (Knobby) 

 to the range. 



A more general discussion of the data in this section is reserved for a 



*0n the West Virginia side of the Potomac the continuatiou of this range is 

 called the Allegheny Front Ridge. 



