TWO EPOCHS IN THE HISTORY OF CAVERNS
Limestone caverns usually have the form of elongated passages, and, if of large size, the passages frequently exhibit an irregularly inter‐connecting arrangement, with occasional expansions in great chambers or domes. The empty cavern space is commonly only a small fraction, perhaps a fourth or a tenth, of the volume of an enclosing solid. Drip‐stones, hanging from the roof or rising from the floor, may occupy a small or a large part of the cavern space. Supplementary cavern enlargements of later date than the dripstones are rarely seen, except where the roof has collapsed from lack of support. The dripstones would therefore seem to have been formed chiefly after the excavation of their caverns had been essentially completed.
Two chief epochs in cavern history are thus recorded; first, an earlier epoch of solutional or corrasional excavation; second, a later epoch of depositional replenishment. . . .