126 J. L. Campbell— Geology of Virginia. 
many places, especially where it appears along the public roads, 
and in cuts on the railroads. The highest division is much 
variegated in color and texture; the beds of shale are yellow, 
brown and red, while considerable strata of sandstone of argil- 
laceous character are found alternating with the shales. 
Among all these are found beds of very calcareous shales 
passing often into impure limestones that abound in Encrinites, 
Atrypas, Spirifers, etc. The upper member has generally more 
ealeareous beds in it than either of the others. This whole 
region has been greatly denuded, but the sharply rounded, 
and often cone-like hills that are left standing, with deep 
ravines cut out between them, present a striking feature of the 
landscape, and, at the same time, afford the means of an 
approximate estimate of the thickness of the whole series of 
shales, which cannot be less than seven hundred feet. 
Along the faces of many of the hills that have been recently 
denuded by floods in the river and its tributaries, the planes of 
stratification, and of slaty (metamorphic) cleavage, are both well 
displayed—the latter so distinct that an unpracticed eye might 
readily mistake them for the planes of original stratification. 
out four miles west of the Blowing Cave the turnpike 
crosses a ridge called Mair’s Mountain, capped by a low are 
of Oriskany sandstone (8), beneath which are exposures of the 
Helderberg limestones (7) where a small stream has cut its way 
through the ridge. Beyond this ridge we find another syt- 
clinal trough filled with the shales of No. 10, out of which 
rise the waters of the Bath Alum. Near this watering places 
a cave formed by the washing out of the softer bed of Medina 
rocks so as to leave a regular arch which becomes narrower and 
lower toward the rear of the cavern, giving the whole cavity 
the shape of a semi-cone with the dividing plane for the floor. 
This is an object of interest to visitors. Its location is beneath 
the ridge, marked “ Piny Ridge,” on the section. _ 
A mile beyond the Bath Alum, our line begins to ascend the 
te ridge of the Warm Springs Mountain. To the struct 
geologist this presents an object of the highest interest. 
we follow the windings of the turnpike we find ourselves sur- 
rounded first by the débris of the Clinton sandstones and shales 
(6 and 7 are concealed), and as we approach the crest of Piny 
Ridges the Medina sandstones (5a) make their appearance 7 
situ. We are thence conducted by a spur across to the face of 
the main ridges, where the road is cut out of the sandstones, 
exposing their lithological .and fossil features in a very inter- 
esting way. Ripple marks and casts of shells in the brown 
and purple sandstones, and fucoids in the shales, are of frequent 
n reaching the depression of the summit where the road 
