Caves or grottoes are natural fissures in the solid crust of the earth, with walls and a natural roof. They are sometimes of immense extent and depth, and frequently the first excavation is only the vestibule to another much larger and deeper. Eldon Hole, in Derbyshire, has been sounded with a line of more than nine thousand six hundred feet, but without reaching its bottom. A cavern near Frederickshall, Norway, has been estimated at eleven thousand feet in depth. Many caverns are remarkable for various natural curiosities. The most interesting are those in which the dropping of water has caused the formation of stalactites, either suspended from the vaults of the caverns in the shape of long crystals, or assuming fantastic forms on the floor and along the wall. Antiparos and Peak caves in Derbyshire, England, owe their celebrity to those formations. Other caves are strewed with petrified bones, and have evidently been the burial-places of generations of human beings. There are caverns which contain deep pits of water, or wells, of such an extent as to acquire the name of subterranean lakes. In some are the sources, and in others the receptacles, of large streams. In Norway you may sometimes walk upon an arched calcareous floor, and hear the roar of torrents under your feet. In Russia, many caverns have been evidently formed by means of water, and even masses of ice. Fingal’s Cave in the Isle of Staffa, on the western coast of Scotland, is the grandest in the known world. Its sides are formed of majestic columns of basalt, which are almost as regular as if they had been formed by art. These columns support a lofty roof, under which the sea rolls its waves, while the vastness of the entrance admits the light of day to the recesses of the cave. The origin of these basaltic formations is uncertain. The caves of Kirkdale, in England, and Gailenreuth, in Germany, are remarkable for the quantities of bones of the elephant, rhinoceros, and hyena found in them. The mine of fluor spar, in Castleton, Derbyshire, passes through several stalactic caverns. Other caverns in England contain subterraneous cascades. In the Rock of Gibraltar there are a number of stalactic caverns, of which the principal is called St. Michael’s, and is one thousand feet above the sea. The most famous caves of Germany are those of Bauman and Bielstein, in the Hartz.