to "Salses" or mud volcanos, argillaceous cones emitting mud, asphalte, and hydrogen, as at Girgenti in Sicily, and at Turbaco in South America; to the Geysers, hot springs in which, as in those of Iceland, the waters, pressed by elastic vapours, rise in jets to a considerable altitude; and, in general, to all operations of natural forces having their seat in the interior of our planet. In Central America (Guatimala), and in the Philippine Islands, the natives even distinguish formally between water- and fire-volcanos, Volcanes de agua y de fuego, giving the former name to those mountains from which subterranean waters issue from time to time with violent earthquake shocks and a hollow noise.
Not denying the connexion of the different phenomena which have been referred to, it yet appears desirable to give greater precision to the terms employed in the physical as well as in the mineralogical part of geology, and not to apply the word "volcano" at one moment to a mountain terminating in a permanent igneous opening or fiery crater, and at another to every subterranean cause of volcanic phenomena. In the present state of our planet the most ordinary form of volcanos is indeed in all parts of the globe that of an isolated conical mountain, such as Vesuvius, Etna, the Peak of Teneriffe, Tunguragua, and Cotapaxi. I have myself seen such volcanos varying in size from the smallest hill to an elevation of 18000 (19184 English) feet above the sea. But besides these isolated cones there are also permanent openings or craters, having established channels of communication with the interior of the earth, which are situated on long chains of mountains with serrated
