gently observed and recorded. The southern part of Italy has, from the earliest periods of human observation, been subject to violent volcanic action. But previous to the Christian era, no record or tradition of eruptions from Vesuvius existed. The summit of the cone, called Somma, was encircled with vines, and its sides were covered with

luxuriant vegetation. At its base were large towns, among which were Herculaneum and Pompeii. At this period, Ischia, Procida, and the Phlegrean fields were the scenes of volcanic eruptions.

53. After a slumber of ages, Vesuvius, in A. D. 63, exhibited signs of internal agitation in earthquakes, which increased in frequency and energy until the year 79, when an eruption overwhelmed the cities Herculaneum, Pompeii and Stabiæ. During sixteen hundred years these cities were buried from human observation and memory beneath volcanic ashes and lava. In A. D. 1713, in sinking a well, some picces of marble and statuary were discovered. This led to extensive excavations in Pompeii and Herculaneum. Fig. 20.

Vesuvius, showing the site of l'ompeii and the River Sarno.

As the former city was buried in ashes and mud, its cxhumation is comparatively casy, and has furnished an immense store of antiquities-paintings and sculptures, linen cloth, household utensils, medicines, loaves of bread with the legi

ble stamp of the baker, papyri, &c., in a perfect state of preservation. Few human skeletons have been found, most of the inhabitants having fled before the irruption. Since that period there have been forty eruptions of Vesuvius, some of which have destroyed towns-as that of 1631 in which lava currents with floods of mud overwhelmed Resina which was built over Herculaneum, and that of A. D. 1784, in which Torre del Greco was encased in lava. The eruption of A. D. 1822, was characterized by violent explosions Fig. 21.

which threw out the lava which had consolidated, altering the shape of the crater, and reducing the height of the mountain from four thousand two hundred to three thousand four hundred feet. The preceding cut presents the appearance of the crater in 1829. The amount of lava ejected by Vesuvius in the eruption of 1794, exceeded twenty-two millions of cubic yards.

54. Etna has been known as an active volcano from the earliest periods of tradition. Its height is ten thousand eight hundred and seventy feet. The base of its cone is eighty-seven miles in circumference, and there are numerous subordinate cones or secondary volcanoes upon the sides of the mountain. More than eighty eruptions of this mountain are recorded, several of which are characterized by the great amount of lava ejected; the whole quantity erupted far exceeding the mass of the mountain. The lava of the eruption of 1669 overwhelmed fourteen towns and villages, with a portion of the city of Catania, running into the sea, and covering eighty-four square miles. Its eruptions sometimes, instead of occurring at its summit, take place through fissures in its sides, which abound with lava dikes.

55. The volcanoes of America are generally distinguished by their great height and number. Within two degrees of latitude from the Equator on either side are nine active volcanic vents, including Cotopaxi, Tunguragua, Antisana and Pichincha, all of which are from sixteen thousand to nineteen thousand feet above the level of the ocean. The whole plain on which Quito stands, nine thousand five hundred feet above the sea, with the adjacent mountains, seems to constitute an immense volcanic dome, embracing six hundred square miles, which is almost constantly agi

tated by internal convulsions, finding vent by eruption at the various craters. Cotopaxi, which rises to the height of eighteen thousand eight hundred and eighty feet, had five great eruptions during the last century, which were heard at distances of from one hundred and forty to six hundred miles on the Pacific coast. Molten lava is rarely raised so high as the summit of these volcanoes, but cinders

and pumice are ejected. The most destructive effects are produced by the torrents of mud and boiling water, which result from the melting of the snow with which the mountain is covered, and the bursting of lakes and subterranean cavities. These currents of mud and water fill the valleys to the depth of several hundred feet, and oftentimes contain so many fishes, that their putrescence renders the atmosphere unwholesome for many miles.

56. In Mexico the transverse band has five active volcanoes, of which Popocatapetl and Jorullo have attracted most attention. Popocatapetl (Smoking Mountain) attains the height of seventeen thousand seven hundred and twenty feet, is snow clad, and continually emits smoke and vapors. 57. The formation of the volcano Jorullo exhibits an