372 Campbell — Rogers's Geology of the Virginias. 



ing about two-thirds of the height presents but gentle dips, so 

 that the two successive formations III and IV (45, c and 5a), 

 of which thej r are composed, are piled upon the subjacent lime- 

 stones in nearly horizontal planes." (p. 218). 



" On the western margin of the valley a narrow belt of forma- 

 tion III extends from the Potomac along the base of Little 

 North Mountain, to its termination in Rockbridge county. It 

 then bends westward a little south of the gap through which 

 flows the North River, and again resuming its course parallel to 

 the Blue Ridge, spreads along the flanks of the main North 

 Mountain and its continuations ; . . . keeping this direction 

 it skirts Caldwell's Mountain, and continues low down on the 

 North or Brushy Mountain, to its termination in Washington 

 county" [on the Tennessee line], (p. 219). 



In the Appalachians of the Virginias are some very interest- 

 ing, and some of them quite extensive and fertile anticlinal 

 valleys, of which the Canadian and Trenton limestones form 

 the bottoms, while the Utica and Hudson slates constitute the 

 lower slopes and spurs of the ridges by which the valleys 

 are bounded. Such are the Crab Bottom in Pendleton and 

 Highland counties, Warm Springs Valley in Bath county, 

 Rich Patch in Alleghany, Sweet Springs Valley in Alleghany 

 and Monroe, and Sinking Creek Valley in Craig and Giles 

 counties. 



The formations of the Canadian and Trenton periods are so 

 frequently accessible to traveling geologists from the same 

 points on railway lines and places of common resort, that we 

 have concluded to note such localities under one general head. 

 In the northeast portion of the Great Valley, the main stem of 

 the Baltimore & Ohio Railway cuts the broad Silurian belt 

 nearly at right angles. About one or two miles west of Harp- 

 er's Ferry station the road passes rather abruptly from older 

 beds to the Canadian limestones and shales, which are exposed 

 in several cuts between that point and Kearneysville. Still 

 farther west the more fossil limestones and shales of 4<z, b, c, 

 come into view as far as Martinsburg and beyond. 



The Valley Branch of the Baltimore & Ohio railway runs 

 for a short distance from Harper's Ferry on the west border of 

 the Cambrian, but soon passes to the Canadian, group which 

 may be conveniently observed at Charlestown and Cameron 

 stations. At Wadesville, and along the banks of Opequon 

 Creek above and below, the exposed rocks are of Trenton 

 age — a part of the irregular synclinal belt which 25 miles 

 farther towards the S.W. passes beneath the Massanutten 

 range. Winchester, Woodstock, Harrisonburg, and Staunton 

 are all near the western margin of the Trenton belt of 

 the Massanutten range, and afford conveniently accessible 



