All limestone caves, great and small, were carved by this slow yet irresistible process. The downward flow follows the joints till a lateral “bedding-plane,” or something else, turns the stream horizontally, when there results a widening of the passageway. Should the roof collapse there would be “a tumble-down” within and perhaps a “sink-hole” without. Should the cave cut through from one bedding-plane to another, a series of galleries would result; the upper ones dry as tinder and the lower ones wet with water that finally reaches the drainage level, whence it emerges into some open valley. Occasionally the whirling water bores straight down through all galleries, making what is termed a pit, or a dome, according to the point of view. Standing pools deposit nitrous earth and various other mineral substances. Water trickling through the roof evaporates, each drop laying down its load of the bicarbonate of lime to create a stalactite; or a stalagmite if it first falls on the floor. A general and convenient term is “dripstone,” masses of which are found at almost any crossing of the joint-planes. Should “fixed air” (carbon dioxide), which is fifteen times as heavy as the atmosphere, settle into the lower parts of any cave, it would make visiting dangerous or fatal. But air currents and other causes make every part of Mammoth Cave free from any except the sweetest, purest air ever inhaled. Approaching Mammoth Cave According to an authentic article in the Louisville Courier-Journal for September 29, 1901, the managers of Mammoth Cave, having occasion to examine the records at Bowling Green, found that cave designated as a corner of a section of land in 1797; which antedates by some years the threadbare legend of Houchins and the wounded bear. During the saltpeter times, 1812-1816, elsewhere described, men came and went in carts or on horseback. Seventy years ago Dr. Davidson told the Transylvania University about visiting the “Green River country,” so called in honor of General Nathaniel Green, the hero of Eutaw Springs—not for its emerald tint. He hired a barouche at Henderson and traversed a dozen counties to Mammoth Cave, which Dr. John Croghan had just purchased for $10,000, intending to “clear out the avenues and make them accessible for an omnibus to the distance of three or four miles, and erect a sort of hotel in the Temple” (the old name of the Chief City). Charmingly did Julius Benedict, sixty years ago, narrate the adventures of Jenny Lind and her party, as they went “by the very worst road in the United States, but amid most delightful forest scenery,” from Nashville to Bowling Green, and thence to Bell’s Tavern, that famous old hostelry. The rest of their journey lay along the edge of “jagged, abrupt glens, along sweeping meadows and budding woodlands,” to the queer old building where “Dr. Croghan did the honors of his subterranean dominions in the most agreeable manner.”