191 J. L. and H. D. CamphclJ — Wm. B. Rogeris 



Eogers's series; but in his final chapter, p. 717, he puts the 

 whole of IV and the greater part of V together as constituting 

 the Niagara group (5a, b, c); while he regards the higher calca- 

 reous shales and limestones as representing the Salina period (6). 

 It is gratifying to find him so ready to subordinate his own 

 system of notation and nomenclature to the more generally 

 applicable and altogether superior system now rendered classic 

 in the science through its adoption by the leading American 

 geologists. 



The bold escarpments of Medina and Clinton beds constitute 

 a conspiuous feature in the Little North Mountain and its 

 several outlying ridges, along the western margin of the Great 

 Valley, as may be seen in the Jump and House Mountains of 

 Eockbridge, and in Purgatory and other ridges in Botetourt 

 county. While the dip of these sandstones and the overlying 

 shales is generally toward the northwest, or normal, as far 

 northward as the Jump Mountain in Eockbridge county, an 

 abrupt change occurs at this point, and throughout the remain- 

 der of the range, nearly as far northward as the Potomac, the 

 eastern margins of the beds are either inverted or thrown into 

 a vertical position. This inversion is conspicuous where the 

 C. & 0. Eailway passes through Buffalo Gap, ten miles west of 

 Staunton. 



A number of ridges, essentially parallel with the North 

 Mountain range, lie between it and the outcropping margins 

 of the coal rocks farther west, occupying a belt of mountainous 

 country from 20 to 40 miles in width and more than 300 miles 

 in length. The framework of these ridges is generally the 

 massive sandstone beds of 5a, b, while they are flanked most 

 commonly by remnants of 6, and of several higher groups, as 

 7 and 8. They are remarkable for their numerous anticlinal 

 arches and folds which usually constitute the crests of the 

 ridges ; and for the comparatively wide and shallow synclinal 

 troughs that intervene, and carry the remnants of higher and 

 less durable formations, among which the dark shales of 10 are 

 conspicuous. 



The Clinton beds of this group carry, in many places, valua- 

 ble beds of the fossil and red-shale iron ores, which have been 

 extensively mined in Pennsylvania, Virginia, Tennessee and 

 Alabama, and are noted for the superior quality of iron they 

 yield. 



Salina Group. — The existence of the Salina in the Appa- 

 lachians of Virginia may be regarded as yet an open question. 

 If it has any representative here it is to be found in the calca- 

 reous shales with occasional beds of limestone, mentioned by 

 Professor Eogers under V. But while there is reason to sus- 

 pect that a portion at least of the higher beds of that series 



