24 
ORIGIN OF CAVE LIFE. 
masses of rocks fall in, which interrupt the passage below. Caves, 
however, exist when the strata are horizontal. Their course is 
changed by joints or faults, into which the excavating waters have 
found their way. 
That these caves were formed prior to the postpliocene fauna is 
evident from the fact that they contain its remains. That they 
were not in existence prior to the drift is probable, from the fact 
that they contain no remains of life of any earlier period so far as 
known, though in only two cases, in Virginia and Pennsylvania, 
have they been examined to the bottom. No agency is at hand to 
account for their excavation, comparable in potency and efficiency 
to the floods supposed to have marked the close of the glacial 
period, and which Prof. Dana ascribes to the Champlain epoch. 
An extraordinary number of rapidly flowing Avaters must have 
operated over a great part of the Southern States, some of them 
at an elevation of fifteen hundred feet and over (perhaps two thou- 
sand) aboAm the present level of the sea. A cave in the Gap 
Mountain, on the Kanawha river, Avhich I explored for three miles, 
has at least that elevation. 
That a territory experiencing such conditions was suitable for 
the occupation of such a fauna as the deposits contained in these 
caves reveal, is not probable. The material in Avhich the bones 
occur in the -south is an impure limestone, being mixed Avith and 
colored by the red soil which covers the surface of the ground. It 
is rather soft but hardens on exposure to the air. 
The question then remains so far unanswered as to Avhether a 
submergence occurred subsequent to the development of the post- 
pliocene mammalian fauna. That some important change took 
place is rendered probable by the fact, that nearly all the neotropi- 
cal types of the animals liaAm been banished from our territory, 
and the greater part of the species of all types have become ex- 
tinct. Two facts have come under my observation which indicate 
a subsequent submergence. A series of caAms or portions of a 
single cave once existing on the southeast side of a range of low 
hills among the Alleghany mountains in Wythe Co., Virginia, Avas 
found to haAm been removed by denudation, fragments of the bot- 
tom deposit only remaining in fissures and concavities, separated 
by Amrious inteiwals from each other. These fragments yielded the 
remains of twenty species of postpliocene mammalia.* This de- 
nudation can be ascribed to local causes, following a subsidence 
of uncertain extent. In a cave examined in Tennessee the ossife- 
rous deposit was in part attached to the 7'oof of the chamber. 
Identical fossils were taken from the floor. This might, hoAvever, 
be accounted for on local grounds. The islands of the eastern 
part of the West Indies appear to liaA-e been separated by submer- 
gence of larger areas, at the close of the period during Avhich they 
*See Proceed. Amer. Phil. Soc. 1869, 171. 
