Stevenson.] Z6\) [jan. 21, 



eludes all but the upper part of No. II, or the Chazy of New York, which 

 is placed by Prof. Safford in his higher group. 



These groups are exposed over a great part of the area ; they are the 

 surface rocks in the great Powell valley between Poor Valley ridge and 

 Wallen's ridge ; they are shown in the southerly side of Wallen valley and 

 the northerly side of Powell mountain ; they extend unbroken from the 

 Hunter Valley fault to the crest of Clinch mountain ; and again from Hol- 

 ston fault to the Valley of Virginia. Detailed study of these groups could 

 not be made ; they are faulted and folded in the most perplexing manner, 

 so that in the course of a day's ride across the country one passes again and 

 again over the outcrop of the same beds. But the general features of the 

 higher group and the upper part of the lower can be worked out somewhat 

 rapidly in Moccasin ridge, where the dip is apparently unbroken by a 

 fault. The lower parts of the Knox group are shown in Buckner's ridge. 



The Trenton and Nashville Group. 



This embraces the Hudson, Trenton and Chazy groups of New York. It 

 is well shown in Powell valley, in Wallen's valley, and on the southerly 

 slopes of Copper and Moccasin ridges. A section was obtained in the 

 vicinity of Estillville, Scott county, which is : 



1. Shales with thin limestone, calcareous at base 755' 



3. Limestones and shales 430' 



thus giving a thickness of 1185 feet for the series. A detailed description 

 is given in the chapter on the area drained by Clinch river. The thickness 

 of the shales is nearly the same on the northerly side of Wallen's ridge, 

 where they are well exposed. They are black and more or less fissile at the 

 base, but higher up the color becomes brownish to reddish brown, and the 

 rock is in thick layers. The change to the Medina sandstone is well shown 

 on the crest of Powell mountain, where it is abrupt. A great limestone 

 lies at the base of the group ; it is massive, occurs in beds from 10 to 20 

 feet thick, which are separated by thinner beds of shale. Many of these 

 limestone beds yield a beautiful marble, which is equal to any from the 

 typical localities in Tennessee. 



Fossils are abundant in many parts of the section. 



The Knox Group. 



As in Tennessee, this group is triple ; the upper division, consistmg of 

 cherty limestones and dolomites, is well exposed in Moccasin and Copper 

 ridges, the middle or shaly division and the lower, consisting of calcareous 

 sandstones, are shown in Buckner's ridge and near Clinch river. 



The section of the upper division, as obtained in Moccasin ridge, may not 

 be complete, part of it having been obtained on one road and part of it on 

 another ; there may be a gap of nearly 300 feet. The estimated thickness 

 is about 1750 feet. In the upper half the limestones are more or less dolo- 

 niitic and contain much chert, so much, that in three great beds the chert 

 predominates. These bed§ are ridge making, and they crown the summits 



