The burning mountains, called volcanos, contain in their bowels, sulphur, bitumen, and other matters of an inflammable nature, the effects of which are more violent than that of gunpowder, or even thunder, and have from the earliest ages terrified mankind, and desolated the country. A volcano is an immense cannon, whose orifice is often more than half a league: from this wide mouth are vomited forth torrents of smoke and flames, rivers of bitumen, sulphur, and melted metals, clouds of cinders and stones, and sometimes it ejects enormous rocks to many leagues distance, which human powers united could not move; the conflagration is so terrible, and the quantity of burnt, melted, calcined, and vitrified matters which the mountain throws out, is so great, that they destroy cities and forests, cover fields an hundred and two hundred feet in thickness, and sometimes form hills and mountains, which are only heaps of these matters piled up together. The action of this fire, and the force of its explosion, is so violent, that it produces by its re-action, succussions which shake the earth, agitate the sea, overthrow mountains, and destroy the most solid towers and edifices, even to very considerable distances. These effects, although natural, have been looked upon as prodigies; and although we see in miniature, by fire, effects nearly similar to those of volcanos, yet there is something in grandeur, of whatever nature it may be, that invariably strikes the imagination and influences the mind, and therefore I am not surprised that some authors have taken them for the vents of a central fire, and ignorant people for the mouths of Hell. Astonishment produces fear, and fear is the mother of superstition. The natives of Iceland imagine the roarings of the volcano are the cries of the damned, and its eruptions the effects of the rage of devils, and the despair of the wretched. All its effects, however, arise from fire and smoke: veins of sulphur, bitumen, and other inflammable matters, are found in the bowels of mountains, as well as minerals and pyrites, which ferment when exposed to air or humidity, and cause explosions proportionate to the quantity of inflamed matters. This is the just idea of a volcano, and it is easy for a philosopher to imitate the action of these subterranean fires; for by mixing together a quantity of brimstone and iron filings, and burying them in the earth to a certain depth, a small volcano may be produced, whose effects will be exactly similar; for this mixture inflames by fermentation, throws off the earth and stones with which it is covered, and smokes, flames, and explodes like a real volcano.