Stevenson.] J UZ [August 20, 



the deep red color of the debris covering the outcrop of the limestone, 

 which so often resembles the decomposed outcrop of a limonite bed. 



In Wallen's ridge the limestone has an almost east dip, but in the valley 

 between that ridge and Poor Vallejr ridge it is pressed into veiy close 

 abrupt folds, in which the dips sometimes exceed 60 degrees. In these 

 folds, too, the dip is twisted, so that instead of being east and west, it be- 

 comes first N. W. and S. E., and then N. N. W. and S. S. E. The lowest 

 member of the series is a mass of reddish to yellow shales, which are so 

 distorted that their thickness could not be determined. These, however, 

 are probably only a part of the limestone series. 



Whether or not any shales intervene between the limestone and the 

 Medina sandstone above, was not ascertained, as a concealed interval occu- 

 pies the space between the two formations. These rocks do not come to 

 the surface again towai'd the east until near Clinch river, where Stock 

 creek has eroded a tunnel through a hill of the limestone. In the limestone 

 of Wallen's ridge, Strophomena alternata, Leptmna sericea, OrtMs occi- 

 dentalis and other species characteristic of the Trenton limestone occur 

 abundantly. 



General Structure op the Region between Black Mountain and 



Clinch River. 

 The following diagram. Fig. 3, which is a continuation of Fig. 1, repre- 

 sents the structure of the region between the fault of Poor Valley ridge 

 and Clinch river : 



C.J. a. e. y. 



Fig. 3.— From Poor Valley Ridge to Clinch River, g-.— Hunter Valley. 



The Stone Mountain Fault is the " Clinch River uplift " of Prof. Lesley, 

 which, according to his map of 1872, continues far toward the east and 

 throughout its entire course is the southern and south-eastern border of the 

 coal field. 



The fault to which the mountain is due is sharp ; the Umbral lime- 

 stone on its southern face dips at 70 degrees ; the Serai conglomerate, 

 at more than 80 degrees ; but the dip decreases .with great rapidity, dimin- 

 ishing from 80 to 3 degrees within a very few rods and soon becoming less 

 than 1 degree. Only the lowest rocks of the coal measures are involved in 

 this abrupt dip and of those the projecting portions have been removed by 

 Pigeon and Roaring forks of Powell river within the area visited. 



Looking across the valley from Stone mountain to Powell mountain, one 

 sees at once the relations of the Stone Mountain fault ; for the Poor Valley 

 Ridge fault is represented there only by a gentle anticlinal. The conditions 

 are as shown in Fig. 2, where the dotted lines represent portions which have 

 been removed by erosion ; the whole section, as given in the diagram, is pre- 



