The geological structure of that portion of southern Missouri which lies to the westward of the Archean rocks near the Mississippi River is peculiarly suitable for the development of caverns. The Ozark uplift produced far-reaching undulations, and there seem to have been no violent disturbances which would result in extensive faults, considerable displacements, or a pronounced inclination of the strata. Jointing and pressure cleavage, however, gave rise to innumerable crevices in the limestone, through which percolating surface water found its way into all parts of the formations. By its solvent power this water gradually enlarged the crevices into passages which, multiplying and uniting, drained constantly increasing areas until they formed subterranean streams with a perpetual flow. Thus began caverns; and these grew in depth, width, and height as the rock was eroded and dissolved. Tributary crevices were subject to the same action; and there was finally created by each of these water systems a network of cavities whose ramifications sometimes extend throughout several townships. In time, sections of the roof, here and there, became so thin from the combined erosion taking place both above and below as to be unable to sustain their own weight; the overlying strata fell into the cave, and the volume of water flowing through it was augmented by drainage which had previously been disposed of on the surface. All this had to seek an outlet somewhere, except in those rare instances where it maintains its downward course until, below the level of any open stream it can reach, it encounters an impervious stratum and must lose itself in the deep rocks. Usually, however, it emerges in the face of a bluff or on the side of a hill; and the opening becomes "the mouth of a cave." Occasionally, in such situations, the water continues to flow out; but usually it finds a way to reach a lower level, and so the cave in time [14]becomes dry except for such water as seeps through from the earth immediately above. Sometimes, too, the point of discharge is at or perhaps somewhat below the level of a stream into which it passes; in the Ozarks are numerous very large springs or fountains which by inverted siphon or artesian action are forced up from subterranean streams lying at a greater depth.