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 three miles long, and three-fourths of a mile across. The depth of this chasm was at first about 2000 feet, but as the walls of the crater continued to fall in, it became eventually reduced to less than half that depth. Previous to this eruption, the summit of the cone round the crater had been 4200 feet high; after the eruption its elevation was found to be reduced to 3400 feet. Another eruption took place in 1833, and even as late as 1857 and 1858 has Mount Vesuvius given uncomfortably convincing indications that it continues as much "alive" as ever.

Mount Ætna, in Sicily, rises 10,874 feet above the level of the sea, of which the lower or bottom part, to the extent of some three thousand feet, consists of calcareous beds, associated with lavas and clays; the remaining 7000 or 8000 feet have been formed by successive eruptions from the volcano. The upper 1100 feet consist of the cone of the crater, which rises from an irregular plain, about nine miles in its circumference. The great crater in the summit of this cone is perpetually emitting sulphureous vapours.

One of the most remarkable volcanoes is that of Kilauea, in the Sandwich Islands, which burns continually, and whose crater contains a sea of red-hot melted lava, sometimes several miles in diameter.

The loftiest volcanoes known are those of Orizaba in Mexico, and Antisana and Aconagua in South America, which are from three to five miles in height.