TILE PARTS OF A VOLCANO. It is customary to recognize as the fundamental parts of a volcano: the basal portion or mountain proper; a more steeply rising and conical portion, or 'cone ;' and the pit or basin-shaped depression found on the summit of most active volcanoes and known as the crater—the seat of eruptivity. There is no sharp or fast line delimiting these parts or making them necessary parts of a volcano, for in many there is no separation between the cone and the base proper—or the whole mountain might be said to be the cone —and in seine volcanoes eruption takes place without any opened crater (Giorgios, in Santorin, 186G, Pelee, and some of the ancient pays of Central France). When present, and it is most generally present, the crater occupies a position on the actual summit of the mountain, but its true relation is frequently masked by the breaking away of a portion of the crater-wall, when the caldron appears sub-central or lateral, with its base a considerable distance down the slope of the volcano. True lateral craters or `craterlets' are formed when the main mountain has broken out over its surface supplemental or 'parasitic' cones.
which are sometimes very numermis, as in the ease of Etna. The persistently active Kilauea, situated at the 4000-foot level on the slope of Mauna 1,oi1, is a supplemental crater of that vol cano, but its activity is mostly, if not entirely, in dependent of the mountain on which it is para sitically placed. The size of the crater bears no relation to the height of the mountain carrying it. Orizaba, three and a half miles }doll, has a crater less than 1000 feet in diameter: the crater of Popoeatepetl is hardly more than double that size. On the other Band, II:tient:la, a Hawaiian volcano on the island of Maui, 10.000 feet in height, has n crater (seemingly the largest in the world) 20 miles in circumferenee; and the erater surrounding Aso-San, 5030 feet, in Japan, is perhaps still larger. Again, the size of the crater in no way measures the intensity of an eruption. Krakatoa, Vesuvius, and PeVe, at the times of their greatest paroxysms, had craters of only moderate dimensions, that of Pc being about 2500 feet in diameter.