7fi 



Stevenson.] • ^ (March 18, 



erroneous and that the shales belong to the Umbral or Greenbrier series. 

 These shales are well shown on the various roads crossing Brushy moun- 

 tain in Bland and especially well along the various roads crossing Little 

 Walker, in Pulaski and Montgomery counties. They occasionally con- 

 tain a thin bed of coal, which was seen on Brushy mountain, in Bland, 

 and on the Norfolk and Western railway near Clark's summit, in Pulaski 

 county ; but the bed is of no importance. The rocks are reddish shales, 

 mostly sandy, occasionally compacted into earthy sandstones ; but in 

 nearly all cases the bedding is irregular. So far as observed, these beds 

 are not fossiliferous. 



A silicious limestone, too impure to be used in making lime, occurs 

 under these shales. It is said to be seven or eight feet thick on Stony 

 Fork of Reed creek, in Wythe county : it is rather less on the railroad in 

 Clark's summit cut four miles and a half east from Max Meadows ; and is 

 a little thicker on Brushy mountain, in Bland county. In many ways 

 this is exceedingly suggestive of the silicious limestone which occurs at 

 the summit of the Vespertine in Pennsylvania and it maybe the represen- 

 tative of that rock. This limestone the writer takes to be in all proba- 

 bility the separating bed between the Umbral and the underlying Vesper- 

 tine, but with greater affinity with th? latter. Unfortunately, the only 

 locality where measurements can be made without great expenditure 

 of time is along New river, but there the limestone was not recognized 

 and an arbitrary line had to be assumed for separation of the two groups. 



The variations in the Umbral within South-western Virginia are not 

 without interest. The section obtained in Lee county showed 



1. Shales and sandstone with thin limestone 705' 



3. Limestone and calcareous shales 150' 



3. Cherty limestone 200' 



In Brushy mountain of Washington county on north side of the Salt- 

 ville fault, the upper division retains its thickness while the lower divi- 

 sions increase vastly, the measurements being. 



No. 1 800 feet. 



No. 2 1470 " 



No. 3 605 " 



But in western Smyth county, where the group is crossed by the road 

 leading to Saltville through Brushy mountain, there is manifestly a seri- 

 ous decrease in thickness of the limestones, while tlie shales appear to 

 have decreased very slightly. Within Bland county, in the same moun- 

 tain, the red shales are found thick, but the limestone has disappeared. 

 This is simply the condition which one should expect to find here, when 

 it is remembered that on the north westerly side of the Great Valley in 

 Pennsylvania and Maryland, limestone is found almost wholly absent 

 from the isolated patches of Umbral : similarly, with the disappearance of 

 the calcareous matter, the fossils disappear. Prof. Fontaine came to the 

 same conclusion with respect to the relations of these shales after com- 



