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 another 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 Halm,* 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. 

 Bui., Vol. XV, No. 3. Aug. 1908, p. 190. 



