Page:Popular Science Monthly Volume 67.djvu/564

558 Methana in the Argolis peninsula, which happened about the year 282 B.C., likens the process to the inflation of a bladder: "The earth," he says, "became distended by the force of impregnated vapor like a bladder filled with air, or like the skin of a goat." A like influence is betrayed also in the beautiful poem of Lucretius, where the following explanation is offered (VI., 639-702): "Ætna emits its flames in this way: caverns of rock run under it, full of wind which heats first itself and then the rocks with which it comes in contact, and then bursts out with flame, ashes, smoke and huge stones. Again, caverns reach from the sea to the mountain; through these pass from the sea both water and wind mixed; this wind and water force up flame and rocks and clouds of sand."

By more careful observation of these occurrences it was further established that volcanoes served as a vent in consequence of which the frequency and violence of earthquake shocks were diminished. Thus, Strabo remarks that the destructive shocks to which the island of Eubœa was subject, ceased when an eruption took place in the plain of Lelanto, near the city of Chalcis. Again, he explains the cessation in Southern Italy of any such convulsions as were supposed to have separated Sicily from the mainland by the formation in that region of cones of eruption, like those of the Lipari Islands. Elsewhere he uses the term of 'breathing holes' in reference to such cones. That he had a clear understanding of this feature is evident from the following passage:

But now these mouths being opened, through which the fire is drawn up, and the ardent masses and water poured out, they say that the land in the neighborhood of the Straits of Sicily rarely suffers from the effects of earthquakes; but formerly all the passages to the surface being blocked up, the fire which was smouldering beneath the earth, together with the vapor, occasioned terrible earthquakes, and the regions being disturbed by the force of the pent-up winds, sometimes gave way, and being rent, received the sea, which flowed in from either side; and thus were formed both this strait and the sea which surrounds the other islands in the neighborhood.

Notwithstanding our indebtedness to Strabo for many interesting details concerning Etna and other volcanic districts, to say nothing of his luminous remarks on the elevation and subsidence of land-masses, he does not seem to have advanced any original explanations of physical phenomena, but merely to have re-echoed those of his predecessors, foremost of whom were Aristotle and Posidonius. Indeed, it is no exaggeration to say that nearly all of Strabo's physiographic ideas were inspired directly by these marvelously keen investigators. The