1887.] ^' [Stevenson. 



but they are thin. These shales are hard enough to form bluffs ; where 

 they have been long exposed to the weather, their surface becomes very 

 dark and the dismal effect is increased by the abundant growth of ashen 

 lichens, which are never absent from the older outcrops. The thickness 

 of the group cannot be determined without careful study, as at all locali- 

 ties crossed the beds are badly folded ; but it cannot be less than six hun- 

 dred feet. 



The Potsdam forms the great mass of Lick mountain ; is the sandstone 

 of Draper mountain ; and is found along the southern border of Wythe, 

 Pulaski and Montgomery counties. The upper beds are alternations of 

 sandstones and shales. Tlie sandstones are mostly white, vary from 

 slightly conglomerate to exceedingly fine grain, almost like quartzite ; 

 many layers are hard and on long exposure become beautifully polished. 

 The lower beds shown in the deeply eroded gorges of Lick mountain and 

 on the northerly side of Draper mountain, are sandy shales, mostly gray- 

 ish and often so thickly bedded as to be shaly sandstones. The bottom of 

 the group is found not far from the line of Grayson and Carroll counties, 

 but that line was not reached by the writer. No measurement to deter- 

 mine the thickness of the group was attempted, as the bottom is not exposed 

 in either Draper or Lick mountain, but in Draper the thickness is not less 

 than 2000 feet, the calculation .being based on the dip and a rough esti- 

 mate of the horizontal distance through the mountain from the fault to the 

 bottom of the Knox shales. The amount of rock exposed along the road 

 traveled over Lick mountain is not so great, but the deeper ravines of that 

 mountain should show an equally extensive section. 



No fossils were observed in the Knox or Potsdam shales, but the search 

 for them was not diligent. Some layers of sandstone near the bottom of 

 the Potsdam sandstone yield Scolithus linearis aljundantly on Lick moun- 

 tain ; but neither that nor any other fossil was seen in the Potsdam of 

 Draper mountain. 



Ores of manganese and iron are reported as occurring near the bottom of 

 the Knox shales, but no effort has been made to develop these except in a 

 small way on Lick mountain. 



IIL THE REGION NORTH FROM BIG WALKER'S MOUNTAIN, 

 BLAND AND GILES COUNTIES. 



In descending Walker's mountain by the Wythe and Tazewell pike, one 

 leaves the Medina at the summit and comes to a fossiliferous bed at barely 

 one hundred feet vertically below the mountain crest. This is from six to 

 eight feet thick and contains many typical Hudson fossils in great num- 

 bers ; Bhynchonella increbescens, Orthis occidentalis (?), Avicula emacerata, 

 Ambonychia radiata, Modiolopsis with fragments of Orthoceras were col- 

 lected within a few moments. Other fossiliferous beds were seen lower 

 down the slope, but no specimens were taken. These reddish shales with 

 streaks of sandstone pass gradually into the yellowish shales of the Hud- 

 son, which in turn pass into the dull reddish calcareous shales or shaly 



