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Page:Popular Science Monthly Volume 24.djvu/38

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THE POPULAR SCIENCE MONTHLY.

Epomeo became tranquil after Vesuvius resumed its eruptions; and for long series of years the island of Ischia had no other outlets for the escape of the gases generated in its depths than its thirty or forty thermal springs, which have contributed, together with the pure air and the beauty of the situation, to increase every year the crowd of visitors.

Every indication tends to support the belief that Ischia, a rival to Vesuvius in the height of its volcano, is an ancient cone composed of the matter thrown up by extremely violent submarine eruptions which took place before the present epoch. As the mountain increased in height through the successive accumulations of the trachytic projections from the central crater, the weaker parts of its flanks, yielding to the height of the liquid column in the vent, were cleft in every direction; the injection of lavas into all the fissures thus formed giving rise to the flows we have just mentioned, melted in with and consolidated the structure, which is thus the result of a protracted alternation of projected débris and flows of compact lavas. We can in this manner account for the disposition of the grand ravines which, descending from Epomeo, plow the flanks of the mountain to a great depth.

PSM V24 D038 Coast of ischia seen from the west.jpg
Fig. 2.—Coast of Ischia, been from the West, Point Comacchia.

The island has, therefore, been progressively raised above the waters, and has grown laterally during the historic period, as is testified by the flows of lava still visible on the Arso and on Monte Tabor, which are prolonged to the sea, and by the numerous secondary cones scattered over its plateaus. It definitely acquired its present relief toward the beginning of this century. Since that time, Mount Epomeo has not given any other signs of its volcanic character than those which the scientific observer might deduce from the analogy of its form with the forms of other volcanoes. Its arid, slashed summit, looking up to the sky, served as the end of the promenade for the numerous visitors who every summer frequented the thermal stations at Casamicciola, Castiglione, and San Lorenzo. Its springs, highly endowed with thermal qualities, and the exceptional fertility of its volcanic soil, on which small shrubs became arborescent, would have sufficed to give to the fortunate, healthful, and gay island great wealth, had not its earthquakes always caused apprehensions.

These disturbances of the earth, the relations of which with the volcanic structure are most evident have repeatedly brought frightful disasters upon Ischia. Hardly a trace of the splendid Roman structures once built upon it now remains; without mentioning specifically