222 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
are outlying members of the numerous mountain groups in the Appa¬ 
lachian mountain province. As the Blue Ridge escarpment and its 
equivalents in South Carolina and Georgia are generally taken as 
the boundary between the Piedmont plateau and the Appalachian 
mountains as far southwest as Gainesville, Georgia, it will be seen 
that much of the higher peneplain is thus included in the latter 
province. 
The Appalachian mountains consist of the folded gneisses, schists,, 
and granites of the crystalline belt which were not reduced to base 
level by the erosion which formed the Piedmont plateau, and contain 
the highest peaks of the southern States. 
Summary .— The more important of the foregoing physiographic 
features, in relation to the present problem, may be summed up as. 
follows. The region of the supposed river capture lies on the west¬ 
ern border of the Piedmont plateau and the eastern border of the 
Appalachian mountain belt, in western South Carolina and north¬ 
eastern Georgia. Through the region passes the southwestern con¬ 
tinuation of the Blue Ridge escarpment, which joins the discordant 
levels of an upper and a lower peneplain surface. It was a stream 
(the Chattooga-Chattahoochefe River) formerly flowing on the upper 
surface, which is believed to have been captured by a stream (the 
Tugaloo-Savannah River) undermining it from the vantage ground 
of the lower level. 
Geology of the Tallulah District. 
Having now considered the general relations of the Tallulah dis¬ 
trict to the broader geologic and physiographic provinces of the 
southeastern United States, I desire to present a short account of 
the more detailed geology of the immediate area under discussion. 
It is not necessary to burden this paper with a long account of all 
the features observed in the field, nor with much that is of interest 
from a strictly geological point of view. But an understanding of 
the general lithologic and structural features of the area is absolutely 
essential to a proper interpretation of many points involved in the 
problem before us. I shall therefore describe briefly the different 
rock types represented in the district, and outline their general areal 
distribution and structural relations. 
