Chapter XV.

Of Earthquakes.

Thales and Democritus assign the cause of earthquakes to water. The Stoics say that it is a moist vapor contained in the earth, making an irruption into the air, that causes the earthquake. Anaximenes, that the dryness and rarity of the earth are the cause of earthquakes, the one of which is produced by extreme drought, the other by immoderate showers. Anaxagoras, that the air endeavoring to make a passage out of the earth, meeting with a thick superficies, is not able to force its way, and so shakes the circumambient earth with a trembling. Aristotle, that a cold vapor encompassing every part of the earth prohibits the evacuation of vapors; for those which are hot, being in themselves light, endeavor to force a passage upwards, by which means the dry exhalations, being left in the earth, use their utmost endeavor to make a passage out, and being wedged in, they suffer various circumvolutions and shake the earth. Metrodorus, that whatsoever is in its own place is incapable of motion, except it be pressed upon or drawn by the operation of another body; the earth being so seated cannot naturally be moved, yet divers parts and places of the earth may move one upon another. Parmenides and Democritus, that the earth being so equally poised hath no sufficient ground why it should incline more to one side than to the other; so that it may be shaken, but cannot be removed. Anaximenes, that the earth by reason of its latitude is borne upon by the air which presseth upon it. Others opine that the earth swims upon the waters, as boards and broad planks, and by that reason is moved. Plato, that motion is by six manner of ways, upwards, downwards, on the right hand and on the left, behind and before; therefore it is not possible that the earth should be moved in any of these modes, for it is altogether seated in the lowest place; it therefore cannot receive a motion, since there is nothing about it so peculiar as to cause it to incline any way; but some parts of it are so rare and thin that they are capable of motion. Epicurus, that the possibility of the earth's motion ariseth from a thick and aqueous air under the earth, that may, by moving or pushing it, be capable of quaking; or that being so compassed, and having many passages, it is shaken by the wind which is dispersed through the hollow dens of it.