Page:Popular Science Monthly Volume 67.djvu/563

Rh by movements of the underlying support of the earth's crust, the next to expound their origin was Anaximander, always supposing that the disciple of Thales has not been confused with some later writer in the following passage from Ammianus (xvii. 7, 12):

Anaximander says that the earth when burnt up by excessive heat and drought, and also after excessive rains, opens larger fissures than usual, which the upper air penetrates with great force and in excessive quantities, and the earth, shaken by the furious blasts which enter those fissures, is disturbed to its very foundations; for which reason these fearful events occur either during periods of dryness, or else after unusually severe rainstorms. And for this reason the ancient poets and theologians gave Neptune the name of Earth-shaker, since he presided over the moist element.

Neither Anaximander, Archelaus nor Xanthus is mentioned by Aristotle in connection with earthquakes or volcanoes, although their opinions have been preserved by other writers. Briefly, the two leading theories before Aristotle's time to account for seismic movements were these: The first, which is attributed to Anaximines, referred them to fractures in the earth's crust which were produced by its passing through a process of drying, after having been previously saturated with moisture. The other was that of Anaxagoras, who believed that they were caused by the fiery elements of the ether, as well as by confined masses of water, which had penetrated into the interior of the earth, and were struggling to escape thence. In a modified form of the same theory, Democritus and Archelaus attached special significance to confined air as a cause of earthquakes, and this agency was still further insisted upon by Aristotle.

It will be noted that both of these theories contain potential germs of suggestion. That of Anaximines, according to which the crust caves in, owing to the splitting of underlying rocks after periods of extreme dryness, foreshadows the modern contraction hypothesis. Excluding, as this view does, the idea of any connection between seismic and volcanic disturbances, the later theory of Anaxagoras directly favors it; and in the hands of the great Stagyrite this connection became the leading feature in the discussion of the question. According to Aristotle, both forms of subterranean disturbances were due to the action of winds (or gases, as we should probably say) which were confined beneath the earth's surface and were endeavoring to find a vent. The element of fire which appears in volcanic eruptions was explained at the result of vapors becoming rarefied and thereupon igniting. Imperfect as this theory may seem, it subsequently met with general acceptance and after slumbering for many centuries, was revived by Cecco d'Ascoli, contemporary of Dante, when Italy again caught the reflection of Greek learning. Posidonius, Strabo, Ovid, Pliny, and the unknown author of 'Ætna' whom some have sought to identify with Lucilius junior, all were influenced by Aristotle's view. Ovid, for instance, in his description of the upheaval of the promontory of