120 J. L. Campbell— Geology of Virginia. 
sections that nature has opened up to our view on a grand scale 
—where the geologist may revel, or the student of science find 
interesting and profitable employment for many days together. 
It passes through or near several mountain gorges of consider- 
able depth and extent, as well as many points of minor inter- 
est, where mountain streams have cut their channels through 
the lower hills and thus exposed the various formations along 
its lines. 
On my former section the series of Professor Rogers was 
given with sub-divisions; and a table appended to present a 
comparison of these with the corresponding periods and epochs 
given in Professor Dana’s Manual, so far as the equivalents 
have been definitely determined in this part of the Appalachian 
chain. On the section accompanying the present paper, the 
numbers and letters refer to Professor Dana’s system. 
Beginning, then, with the southeastern extremity, near the 
Rockbridge Baths, we find a natural section cut by the North 
River through a part of 3 a and the whole of 3b and «, ete. 
(Calciferous, Quebec and Chazy=No. II Rogers). In the imme- 
diate vicinity of the Baths these formations are very much 
obscured by the Quaternary deposits of drift from the moun- 
tains above, but they may be studied conveniently at points a 
mile lower down on the river cliffs, or on the neighboring hills 
a little remote from the river, on the southwest side, where the 
section passes. For a description of the rocks of this period, 
the reader is referred to the number for July. : 
The line of fault presented on the former section continues, 
with a single interruption, some distance beyond the present 
section, crossing the river a short distance above the Baths 
(N.W.)—the older (3) being still thrust — over the edge 
of the newer (4 a.) This junction of the displaced strata can be 
seen indistinctly along the river banks at low water, but may be 
more distinctly traced in the hills southwest of the river, and 
on Hays’ creek northeastward. aoe 
This fault has doubtless much to do with determining the 
~ temperature of these thermal Baths, the waters of which have 
a temperature of 72° F., and are kept in gentle but constant 
agitation by escaping bubbles of gas, consisting largely of 
nitrogen and carbonic acid. The remedial virtues of the Baths 
have been long recognized. As we pass up the river in 4 
northwesterly direction we soon find the Trenton limestones 
forming the bottom of the river-bed where the strike of the 
strata can be distinctly seen crossing the stream nearly at right 
angles. The same rocks also crop out on the eS 
hills, which gen have a rounded shape and are strewed 
with quantities of lien! drift from the adjacent mountain 
gorges. There are no cliffs here; for these argillaceous lime- 
