400 



PALEOZOIC TIME. 



At the west base of the Chilhowee Mountain, near Montvale 

 Springs, Blount County, Tennessee, Subcarboniferous shales are 

 brought into contact with the " Ocoee " conglomerate of the Acadian 

 epoch, by a fault and displacement of more than 10,000 feet. (Saf- 

 ford.) 



Lesley, after explaining the relations of the eastern or Blue Ridge, the Great Valley- 

 next west, the Appalachian or middle chain, and the Alleghan}'- or western, and men- 

 tioning that the eastern escarpment of the last, "overlooking the Appalachian ranges 

 with their narrow parallel interval-valleys, is the so-called Backbone Alleghany Moun- 

 tain," and separates the head waters of nearly all the Atlantic and Western rivers, 

 observes that New River, in southern Virginia, divides the northern region of plica- 

 tions from the southern of great faults; and this river is remarkable for cutting 

 through the Appalachians, and taking its rise even as far east as the Blue Ridge. He 

 adds, concerning this southern district, " The Paleozoic zone, included between the 

 Great Valley and the Backbone escarpment, is occupied by as many pairs of parallel 

 mountains as there are great pai-allel faults; and, as these faults range in straight 

 lines, at nearly equal distances from each other, these mountains run with remarkable 

 uniformity side by side for a hundred or two hundred miles, and are finally cut off, 

 either by short cross-faults, or by slight angular changes in the courses of the great 

 faults." This strip of country is thirty to forty miles wide; and the intervals between 

 the fractures or faults are from five to six miles wide. All the ranges show southeast 

 dips; a portion of the Carboniferous formation forms the southeastern brow of each, 

 overlooking to the southeast Lower Silurian limestone, and resting on Devonian and 

 Silurian, which come into view to the northwest. 



According to the Professors Rogers, these faults in southwestern Virginia, which 

 were early described by them, occur along the axes of plications, instead of in mono- 

 clinal strata. (Trans. Amer. Assoc. Geol. Nat., p. 494.) 



Thus, the whole Continental border, from Alabama to Newfound- 

 land, participated in these grand movements. 



3. Alterations of rocks. — The alterations which the rocks under- 

 went at the time of these disturbances are as follow : — 



1. Consolidation. — Strata were consolidated ; for the rocks of the 

 Coal-measures, the conglomerates and sandstones especially, are often 

 very hard and siliceous, where the beds have been most folded or 

 disturbed. 



2. Debituminization of Coal. — The coal is not bituminous, or is 

 true anthracite, where the rocks are most disturbed ; and, going west- 

 ward, into regions of less disturbance, the proportion of bitumen or 

 volatile substances increases quite regularly (Rogers). It appears as 

 if the debituminization of the coal had taken place from some cause 

 connected with the uplifting. In Rhode Island, the effects are still 

 more marked, the coal being altered not simply to an excessively hard 

 anthracite, but in part to graphite. 



3. Crystallization or Metamorphism. — In some districts, the rocks 

 are changed to gneiss, mica schist, or slates, and granular limestone 

 (marble). 



4. Characteristics of the force engaged. — As in the Medio- 



