Stevenson.] Zd4 [ja^. 21, 



is certainly less. The lower shales are often very rich in carbonaceous matter 

 and two beds near the base have been mistaken for coal beds. Iron pyrites 

 occurs plentifully in these lower shales at all localities and alum incrusta- 

 tions are common. A fine-grained, nearly white sandstone is shown at 

 several places near the base of the group ; it is a good flrestone and has 

 been hauled nearly forty miles by wagon, for use as furnace lining. 



Few fossils were seen in the Hamilton ; a Ghonetes occurs plentifully in 

 the upper shales and imperfect specimens of Lingula Avere found in the 

 lower shales. These Hamilton beds are the black shales described in Prof. 

 Safford's report on Tennessee. 



The Upper Silurian. 



This is represented bj'' the Oriskany, Lower Helderberg, Clinton and 

 Medina ; the Niagara and the Oneida Conglomerate were not recognized. 



The OrisTcany. 



This is a sandstone, probably not more than 35 or 40 feet thick, which is 

 shown in the Poor valley of Powell river, and along the vallej'^s of Wildcat 

 creek and the North Fork of Clinch ; also along the latter stream at the 

 foot of Powell mountain, and in the Hunter valley at Stony creek. It is 

 absent along the southerly foot of Clinch mountain, where, indeed, the 

 Upper Silurian is represented only by the Medina and a small part of the 

 Lower Helderberg. 



The Oriskany sandstone is coarse, reddish on exposed surface but white 

 on the fresh surface. It is friable, and at some localities, notably along 

 the North Fork of Clinch rivei', it readily disintegrates on exposure. Very 

 possibly the upper ore-horizon along Wildcat creek and the North Fork 

 of Clinch river may belong in part to this sandstone. This rock con- 

 tains Streptorliynclms Jii'pparionyx on Stony creek ; in the Poor valley of 

 Powell river, it contains Merista lata, but with that there occur some forms 

 belonging to the Lower Helderberg, so that in the writer's previous 

 memoir the sandstone was referred to the lower group. The relation be- 

 tween the two groups is very close throughout this region. 



The Lower Helderierg. 



This group accompanies the Oriskany. In a general way its character- 

 istics are very similar to those of the same group in New York, The 

 Leperditia bed at the base is shown near Big Stone gap. Below this is a 

 coarse sandstone like the Oriskany, which is shown at some localities 

 along Powell river, and is well exposed along the line of the Pattonsville 

 fault. The group closes with a limestone, which frequently becomes 

 silicious. It is occasionally fossiliferous and the species are very charac- 

 teristic. 



The lower sandstone of this group is ferriferous and occasionally holds 

 a brown hematite of excellent quality. A fossiliferous brown hematite 

 was seen at the southerly foot of Clinch mountain, which, in all proba- 

 bility, should be referred to this group. 



