Volcanic Mountains—Extinct and Active Craters—Their Size—Dangerous Crater-explorations—Dr. Judd in the Kilauea Pit—Extinct Craters—Their Beauty—The Crater of Mount Vultur in Apulia—Volcanoes still constantly forming—Jorullo and Isalco—Submarine Volcanoes—Sabrina and Graham’s Island—Santorin—Number of Volcanoes—Their Distribution—Volcanoes in a constant state of eruption—Stromboli—Fumaroles—The Lava Lakes in Kilauea—Volcanic Paroxysms—Column of Smoke and Ashes—Detonations— Explosion of Cones—Disastrous Effects of Showers of Ashes and Lapilli— Mud Streams—Fish disgorged from Volcanic Caverns—Eruption of Lava— Parasitic Cones—Phenomena attending the Flow of a Lava Stream—Baron Papalardo—Meeting of Lava and Water—Scoriæ—Lava and Ice—Vast Dimensions of several Lava Streams—Scenes of Desolation—Volcanoes considered as safety-valves—Probable Causes of Volcanoes. Volcanoes are vents which either have communicated, or still communicate, by one or several chimney-like canals or shafts, with a focus of subterranean fire, emitting, or having once emitted, heated matter in a solid, semi-liquid, or gaseous state. The first eruption of a volcano necessarily leaves a mound of scoriæ and lava, while numerous eruptions at length raise mountains, which are frequently of an amazing extent and height. These mountains, which are generally called volcanoes, though in reality they are but an effect of volcanic action situated far beneath their base, are called _extinct_ when for many centuries they have exhibited no signs of combustion—_active_, when, either perpetually or from time to time, eruptions or exhalations of lava, scoriæ, or gases take place from their summits, or from vents in their sides. Their shape is generally that of a more or less truncated cone; but while some, like Cotopaxi or the Peak of Teneriffe, rise with abrupt declivities in the shape of a sugar-loaf, others, like Mauna Loa in the island of Hawaii, gradually, and almost imperceptibly, ascend from a vast base embracing many miles in circuit. Their heights also vary greatly. While some, like Madana in Santa Cruz, or Djebel Teir on the coast of the Red Sea, scarcely raise their summits a few hundred feet above the level of the ocean, others, like Chuquibamba (21,000 feet), or Aconcagua (22,434 feet), hold a conspicuous rank among mountains of the first class.