182 
Often the water does not evaporate right at the base of the joint but 
trickles down the side walls, depositing a coating of calcareous material 
there. 
In Milroy’s Temple, Wyandotte cave, and in Shawnee cave, Law- 
rence County, the evaporation has not always taken place at the lower 
end of the stalactite, but they are curved outward and upward. This is 
possibly due to the twining tendency in the crystallization of the calcite. 
Local conditions may give rise to an almost endless variety of these cal- 
careous deposits. 
Under certain conditions gypsum and epsomite are deposited in caves, 
the former as a coating of the walls and as curved crystals or ‘“Oulopho- 
lites,’ and the latter as delicate needle-shaped crystals in the earth of 
the cave floor. H. C. Hovey in the “Manual of the Mammoth Cave of 
Kentucky” states that the black deposit on the ceiling of the Star Cham- 
ber of this cave is the oxide of manganese. All of these materials are 
derived from the Mitchell limestone, but owing to its purity are not nearly 
in such great abundance as the calcite deposits. 
The materials deposited on the floors of caves are generally of three 
classes: fallen rock, chert gravel and nitrous earth. Of the first class 
there is little to be said, as it has already been mentioned. The chert 
is derived from the concretions of chert in the limestone. Owing to its 
insolubility, it remains after all other materials have been dissolved. In 
Shawnee cave, Lawrence County, it has in places been cemented together 
by calcite and some oxide of iron to form a hard, firm conglomerate. 
The nitrous earth or “saltpeter dirt” is practically always found in 
passages now abandoned by the streams which formed them. It seems 
to have been originally the finer portion of the solid matter carried by 
the cave stream. Some slackening of the current, probably due in most 
cases to fallen rock, caused this material to be deposited. The deposition 
then continued until the stream found anotlfter outlet. Another source of 
this fine earth, and probably equally as important, is that of material 
washed in through crevices and small sink-holes to the passages directly 
beneath them, which, of course, would be the higher passages of the cave. 
Now these high and dry passages are the ones most liable to be frequented 
by bats, and it is probably from the dung of these animals, which, ac- 
cording to Hahn,* spend about five-sixths of their existence in a dormant 
state, that the potassium nitrate is derived. Inspection of the earth in a 
*Hahn, W. L., Some Habits and Sensory Adaptations of Cave-inhabiting Bats. Biol. 
Bul., Vol. XV, No.3. Aug. 1908, p. 190. 
