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20. GEOLOGY. 
Entrance of the Mammoth Cave of Kentucky. 
The Caves of Kentucky. By C. S. 
Rafxnesque. 
Among the various and curious 
geological phenomena of Kentucky, 
the numerous Caves of that region 
are not the least interesting. They 
have attracted long ago the atten- 
tion of travellers and Geographers; 
but I was the first to examine them 
geologically and zoologically, from 
1818 to 1826. 
In the last war, between 1812 and 
1815, they became of some impor- 
tance by affording a good deal of 
Saltpetre by lixiviation of their soil. 
But all did not afford it, some con- 
tained a mere stone floor, or stalag- 
mites, or a diluvial clay. 
Their number is unknown, be- 
ing too many for enumeration; per- 
haps fifteen hundred or more; of all 
sizes from ten yards to ten miles 
in extent. They are found chiefly 
in the limestone region or the cal- 
careous strata; but the greatest 
number is situated in the central 
hilly region of Kentucky, where the 
limestone is covered by sandstone 
and slate hills ; being however 
found in the lime below, visible in 
valleys ; seldom in the sandstone 
itself. They extend through the 
three kinds of limestone, the €her« 
ty, the Specular, and the Compact, 
chiefly this last. These limestones 
being of the oldest secondary or or- 
ganic formation, called transition 
by some Geologists ; but perfectly 
horizontal without any visible dip 
for 100 miles. 
These various Caves are of seven 
different kinds, which I call 
1. Cliff Caves, commonly called 
Rock Castles or Rock Houses in 
Kentucky. They are merely natu- 
ral excavations in the cliffs of riv- 
ers, somewhat like chambers, al- 
ways small, without stalactites, nor 
saltpetre. Common in East Ken- 
tucky, and on Rock-castle river, 
which takes its name from them. 
Not uncommon in sandstone and 
freestone. 
2. Fissure Caves , found chiefly 
in the slaty or shaly claystone 
and coal region, being horizontal 
or vertical fissures in the strata, 
often without any communication 
with the outside. Rather rare, often 
concealed. 
3. Sinking Caves . The outlets 
of the numerous Sinking Creeks, 
