J. L. Campbell— Geology of Virginia. 125 
of lime (septaria), increase in size and number; while thin beds 
of fossil limestone, especially in a, are occasionally exposed to 
view. 
At Millboro depot a line of stages leaves the railroad for the 
Warm Springs, fifteen miles to the west. At the distance of 
two miles we reach the old Millboro Springs where we again 
feecrtste strata (10). 
banks of the Cow-pasture both above and below the passage 
through Cave Hill. A short distance below, in what is called 
“Alum Bank,” we found a thin bed of limestone remarka 
Near this place is one of the numerous so-called “ Alum 
Springs”—the Wallawhatoola, an old Indian name. The waters 
here, as at the Rockbridge and the Bath Alum Springs, collect 
slowly from the crevices of the dark pyritous shales of No. 10. 
Springs of this class are very numerous among the Devonian 
shales in Virginia; and waters of similar character sometimes 
issue from shales of earlier and later dates. Their chief min- 
eral constituents are sulphates of alumina, lime, magnesia, ~ 
potassa, soda, iron (ferrous sulphate), with more or less free sul-_ 
phuric acid. In the Wallawhatoola I found, with the spectro- 
ey a decided trace of lithia. : mele 
he shales of this region, and especially in this valley of 
e ¢ i character- 
black, sometimes bluish-black—shales that split readily into 
thin layers, and even fine scales or slender columnar fragments. 
The middle member has a decidedly greenish tint—olive in 
*This is No. VIII of Professor Rogers’s series. 
