1881.] -^"5 [Ste veil son. 



The Clinton. 



Prof. SaflFord has found in Tennessee above the Clinton group a lime- 

 stone, which he regards as representing the Niagara group of New York ; 

 but no traces of that limestone were observed by the writer, unless the 

 fragments seen on the Jonesville and Gladosville pike and belonging in the 

 concealed interval between rocks of Clinton, and those of Lower Helder- 

 berg age, may be referred to it. Elsewhere no bed was seen which could 

 be regarded as representing the Niagara group. 



The Clinton group is present in Poor Valley ridge ; on both Wallen's 

 ridge and Powell mountain ; and at two localities along the northerly side 

 of Buckner's ridge ; but it is absent from the southerly side of Clinch 

 mountain. The structure of that ridge is shown in Moccasin gap, 

 where the Medina sandstone underlies the Lower Helderberg, on which 

 the Hamilton shales rest. 



No full section of the Clinton group was obtained, but its thickness can- 

 not be far from 700 feet. The rocks are sandstones and sandy shales, but 

 a calcareous sandstone, 60 feet thick, and containing thin bands of very fair 

 limestone, occurs near the middle of the group. Three beds of the fossil- 

 iferous ore were seen, and, according to Mr. Pennington, who owns the forge 

 in the gap which bears his name, two others exist, but they are very thin. 

 The three beds belong below the middle of the group. The lower two are 

 not far from 50 feet apart, but the interval to the upper bed is somewhat 

 greater. These intervals show considerable variation in Poor Valley ridge, 

 where the ore has been opened at several localities. Two beds were seen 

 on the southerly slope of Wallen's ridge and three on Powell mountain ; 

 while only two are exposed in Hunter valley. The most important bed is 

 the middle one, which usually carries excellent ore. The others vary much 

 in thickness and quality of the ore. 



The Medina Sandstone. 



This is a salient feature of the region, as it forms the crest line of 

 "Wallen's ridge, Powell mountain and Clinch mountain. For the most 

 part, it is a massive, fine-grained and very hard sandstone, but it has some 

 layers of conglomerate, which are most numerous near the top. On Clinch 

 mountain it is divided by bands of shale in which brown hematite occurs. 

 On Powell mountain and Wallen's ridge it graduates upward into a red- 

 dish sandstone which may represent the white oak sandstone of Prof. Saf- 

 ford's report, though the writer is inclined to regard it as part of the 

 Clinton or dyestone group, the total thickness as observed on the several 

 ridges does not exceed 400 feet. No fossils were seen other than casts of 

 the characteristic fucoid. 



The Lower Silurian. 



This is represented by Formations II and III of the Virginia column. A 

 more convenient division for descriiDtiou is that made by Prof. Salford into 

 the Knox and the Trenton and Nashville groups. The Knox group in- 



PROC. AMER. PHILOS. SOC. XIX. 108. 2d. PRINTED FEBRUARY 23, 1881. 



