GENERAL OBSERVATIONS. 



399 



in eastern Tennessee, well shown in the map and sections of Safford. 

 In southwestern Virginia, there are faults, according to Rogers, of 

 seven or eight thousand feet. One remarkable line of this kind ex- 

 tends along the western margin of the Great Valley of Virginia, 

 throughout the chief part of its length, along by the ridge (on the 

 northwest side of the valley) named, in its different parts, the Little 

 North Mountain, North Mountain, and Brushy Ridge. In some parts, 

 as in the annexed section, Fig. 704 (by Lesley), the Lower Silurian 



Fig. 704. 



Section of the Paleozoic formations of the Appalachians, in southern Virginia, between Walker's 

 Mountain and the Peak Hills (near Peak Creek Valley) : F, fault ; a, Lower Silurian limestone; 

 b, Upper Silurian ; c, Devonian ; d, Subcarboniferous, with coal beds. 



limestone is brought into conjunction with beds but little below the 

 Subcarboniferous limestone ; so that there is a transition from the 

 lower strata to the upper, in simply crossing the fault. In some 

 places, there is an inversion of the strata, so that a bed of semi- 

 bituminous coal of the upper beds is found under the Lower Silurian 

 limestone and conformable to it in dip. This fault continues on for 

 eighty miles. (W. B. & H. D. Rogers.) 



Several such examples might be cited from Pennsylvania as well 

 as Virginia. One occurs near Chambersburg, Pa., and is thus de- 

 scribed by Lesley in his " Manual of Coal and its Topography " 

 (p. 147). "The western side of the anticlinal 'cove-canoe' has been 

 cut off and carried down at least twenty thousand feet into the abyss, 

 along a fracture twenty miles in length ; the eastern side must have 

 stood high enough in the air to make a Hindoo Koosh ; and all the 

 materials must have been swept into the Atlantic by the denuding 

 flood. The evidence of this is of the simplest order, and patent to 

 every eye. Portions of the Upper Devonian wall against the lowest 

 portions of the Lower Silurian. The thickness of the rocks between 

 is, of course, the exact measure of the downthrow, which is therefore 

 twenty times as great as the celebrated Pennine Fault in England. 

 Yet a man can stand astride across the crevice, with one foot on 

 Trenton limestone and the other on Hamilton slates, and put his 

 hand upon some great fragments of Shawangunk grit, caught as they 

 were falling down the chasm, held fast in its jaws as it closed, and 

 revealed by the merest accident of lying suspended in the crack just 

 where the plane of denudation happened to cut it." 



