182 



AN AMERICAN GEOLOGICAL RAILWAY GUIDE. (VA.) 



14. The Anticlinal Valley, which includes the group of thermals known as the Warm, Hot, 

 Healing, &c., Springs, closes up about ten miles northeast of this, and its axis subsides towards 

 the southwest in broad spurs which reach the river a few miles be^y Covington, in low arches of 

 7. and 8., overlaid by 10. The heated waters issue at numerous points throughout a distance of 

 thirty miles; from Cambrian and Siluro-Cambrian rocks, 3 c., 4 a., usually inverted aud often 

 faulted along the west side of the valley, the eastern boundary of which is formed by the massive 

 Warm Spring Mountain, 5 a., 5 b., dipping east, while its western limit consists of a narrow, broken 

 ridge of the same formations in a vertical or inverted position. Stages to Healing, Hot and Warm 



.Springs, severally 15, 19 aud 22 miles. Near the first is the Cascade (200 feet) of Falling Spring 

 'Creek, which, cutting through the west M'all of the anticlinal, flows over a mass of calcareous 

 tufa, deposited from the waters. 



The anticlinal of Peter's Mountain, rising a few miles northwest of Covington and exposing at 

 the tunnel 7. and 8., expands towards the southwest, until it opens out into the valley of the Sweet 

 Springs, containing another group of thermals of lower temperature than the preceding. This 

 anticlinal, extending southwest, does not close up, but passes into the great Peter's Mountain and 

 East River Mountain fault, which for a distance of fifty miles brings the Cambrian in contact with 

 the Vespertine and Umbral formation, Sub-Carb., 13 a., 13 b. 



15. The Upper Subcarboniferous, or Umbral shales, here include a considerable thickness of 

 brown and gray flaggy sandstone, the same which forms the hard rock of Swope's Knobs. 



16. About 20 miles northwest of this point (by canal or road) we enter the gorge by which the 

 James River traverses the Blue Ridge, where are exposed fine sections of Archaean rocks, A and B. 

 and of the Cambrian, Primal 2 a., resting unconformably on the western slope of the foi-mer, and 

 occupying the flanking ridges, which adjoin the valley. The Natural Bridge, the remnant of a 

 former tunnel or cave in 3 a. b., is about 8 miles northwest from the upper end of the gap. 



17. A few miles east of this, between Bannister and Dan Rivers, is a small patch of Jurasso- 

 Triassic rocks. 18-17., corresponding to the Farmville or middle belt, (see note 2), and containing 

 Estheria, &c. 



18. This deposit, made up largely of Diatoms, lies near the base, but within the limits, of the 

 Miocene Tertiary. It contains occasional casts of Miocene shells, and is generally overlaid by beds 

 of this formation, and rests either upon or but little above the top of the Eocene. Having 

 formerly traced this deposit from the Patuxent River in Maryland to the Meherrin in Virginia, I 

 liave lately found by an examination of the artesian borings at Fortress Monroe, that a similar 



