Stevenson.] '"'*-^ [Jan. 21, 



Silicious Group. 



17. Limestone 300' 



18. Shale and sandstone 150' 



Total Mountain Limestone group, 855' ; Silicious group, 350'. 



The interval. No 1, is filled for the most part with shale, though there 

 are traces of sandstone and a bed of rather lean carbonate of iron. The 

 latter has been opened by Mr. Pennington, but it is too lean for use in his 

 forge. The shale. No. 3, is quite rich in carbonaceous matter and it may 

 represent the Coal beds of south-west Pennsylvania, belonging at this hori- 

 zon. Nos. 3 and 4 are hard red grits. The interval. No. 5, contains some red 

 shale, some bluish grit-like beds, but for the most part it is effectually 

 concealed. The sandstone, No. 6, is fine-grained, mostly light colored, 

 and the sand is sharp and cleaned. The bed is well exposed on both sides 

 of Pennington's gap and is the first sandstone bed seen in ascending Big 

 Stone gap. It is the principal source of the sand covering the "bottom" 

 of Powell river and that of the North Fork near the gaps. No. 10 is a hard 

 blue grit, containing not a little oxide of iron, which causes disintegration 

 on exposure. It is well shown in the bed of the North Fork in Penning- 

 ton's gap. No. 14 is imperfectly exposed, but here and there it shows some 

 limestone and red shale. Mr. Pennington says that some good iron ore has 

 been obtained from this interval. No. 15 is an excellent limestone, and it 

 would be good either for furnace use or in the manufacture of lime. Chert 

 first appears in the lower part of No. 16, where numerous layers were seen 

 from half an inch to two inches thick and richly fossiliferous. From one of 

 these the following species were obtained during a hurried examination : 

 Fenestella ; Zaphrentis spinuUfera ; Producius semi-recticulatus ; Hemi- 

 pronites crassus ; Spirifera leidyi ; and AtJiyris subquadrata. 



The great limestone. No. 17, is well shown along the southerly face of 

 Stone mountain from Little Stone gap to far beyond Pennington's gap ; 

 and it is well exposed in each of the gaps. The rock is mostly fine-grained 

 and compact, with conchoidal fracture, though here and there a layer oc- 

 curs which is somewhat granular. Some beds contain much chert in no- 

 dules occasionally as large as an orange. Fossils are numerous, but for the 

 most part they cannot be obtained in identifiable condition. Productus 

 eora with an unrecognized Zaphrentis was obtained near the mouth of Big 

 Stone gap. 



No. 18 has been identified by Mr. Moore with the Protean member of 

 the Silicious group of Tennessee, the Knobstone of the old Kentucky re- 

 ports. It is not very well exposed at any locality visited ; but as far as 

 seen, it consists of bluish sandstones, weathering reddish, with some shale. 

 These sandstones are slightly calcareous and some of them are true grits. 

 No fossils were seen in this stratum. 



Poor Valley and Poor Valley Bidge. 

 Under this head may be included not only that narrow area between 

 Stone mountain and the fault of Poor Valley ridge, but also the area 



