Stevenson.] O^ [March 18, 



as well as in Bland county around the foot of Round mountain. They 

 contain little of interest. 



The Upjjer Silurian. 



No definite line of separation between Upper Silurian and Devonian 

 could be made out except in the " "Wilderness " area of Bland and Giles 

 counties ; there the Oriskany is present, which makes the boundary dis- 

 tinct. Upper Silurian, represented by Oriskany, Clinton and Medina, 

 makes up the most prominent features of the district, Medina being, par 

 exeellence, the mountain -making rock. 



The Oriskany was seen only in Bland county, where it is exposed at the 

 foot of Round mountain and the Garden mountains, as well as along the 

 foot of Wolf Creek mountain in the "Wilderness." The rock is a thin 

 sandstone, which resists the weather so well as to make a small ridge. If 

 this rock be present in the "Poor valley " between Big and Little Walker 

 mountains, it must be very thin and must yield readily to the weather, as 

 that valley was crossed on four lines, each aftbrding good exposures, but 

 without Oriskany. As shown in the " Wilderness " the rock is a moder- 

 ately coarse gray sandstone, evidently not more than ten feet thick, and 

 containing, in addition to the ordinary forms, impressions of large crin- 

 oidal joints. 



The Lower Hclderherg may be present in the "Wilderness," but no pos- 

 itive proof exists. Fragments of white chert containing a delicate Stro- 

 matopora, and seen near Round mountain, have much resemblance to the 

 chert bed at the base of the Oriskany or top of the Lower Helderberg. 

 Aside from those fragments nothing referable to the Lower Helderberg 

 was seen in any of the " Poor valleys." 



The Clinton forms a bench around Round mountain ; on the Garden 

 mountains ; on Wolf Creek mountain and its continuation in Pearis and 

 Sugar Run mountains ; ou Big Walker and Cove mountains. Everywhere 

 it presents the same features, variegated shales with white sandstones near 

 the ores. The "fossil'' ore occurs, but little only is known respecting 

 either its quantity or quality. It appears to be abundant, though silicious, 

 on Wolf Creek mountain, if one may judge from the fragments where the 

 ore horizon is crossed by the I'oad near Wolf creek or Rocky gap. 



The Medina is well known as the mountain-making rock. Its outcrop 

 forms the crest of Cove, Big Walker, Garden, Round and Wolf Creek 

 mountains ; it makes a double outcrop on Pearis and Sugar Run moun- 

 tains, as well as on Butte and Salt Pond mountains ; while it is shown on 

 each side of the House and Barn synclinal in Buckhorn and East River 

 mountains. 



The Upper or White Medina is very far from being coarse, though a 

 few layers of conglomerate were observed in it. The best exposure is in 

 the gap made by New river through Big Walker mountain, where the 

 estimated thickness is 375 feet. For the most part the rock is white, and 

 on long exposure the surface becomes beautifully polished. This is char- 



