Anaximander affirms that all these are produced by the wind after this manner: the wind being enclosed by condensed clouds, by reason of its minuteness and lightness it violently endeavors to make its passage; and in breaking through the cloud it gives the noise; and the rending the cloud, because of the blackness of it, gives a resplendent flame. Metrodorus, that when the wind falls upon a cloud whose densing firmly compacts it, by breaking the cloud it causeth a great noise, and by striking and rending the cloud it gives the flame; and in the swiftness of its motion, the sun imparting heat to it, it throws out the thunderbolt. The weak declining of the thunderbolt ends in a violent tempest. Anaxagoras, that when heat and cold meet and are mixed together (that is, ethereal parts with airy), thereby a great noise of thunder is produced, and the color seen against the blackness of the cloud causes the flashing of fire; the full and great splendor is lightning, the more enlarged and embodied fire becomes a whirlwind, the cloudiness of it gives the hurricane. The Stoics, that thunder is the clashing of clouds one upon another, the flash of lightning is their fiery inflammation; their more rapid splendor is the thunderbolt, the faint and weak the whirlwind. Aristotle, that all these proceed from dry exhalations, which, if they meet with moist vapors, force their passage, and the breaking of them gives the noise of thunder; they, being very dry, take fire and make lightning; tempests and hurricanes arise from the plenitude of matter which each draw to themselves, the hotter parts attracted make the whirlwinds, the duller the tempests. CHAPTER IV. OF CLOUDS, RAIN, SNOW, AND HAIL. Anaximenes thinks that by the air being very much condensed clouds are formed; this air being more compacted, rain is compressed through it; when water in its falling down freezeth, then snow is generated; when it is encompassed with a moist air, it is hail. Metrodorus, that a cloud is composed of a watery exhalation carried into a higher place. Epicurus, that they are made of vapors; and that hail and rain are formed in a round figure, being in their long descent pressed upon by the circumambient air. CHAPTER V. OF THE RAINBOW. Those things which affect the air in the superior places of it are of two sorts. Some have a real subsistence, such are rain and hail; others not. Those which enjoy not a proper subsistence are only in appearance; of this sort is the rainbow. Thus the continent to us that sail seems to be in motion. Plato says, that men admiring it feigned that it took origination from one Thaumas, which word signifies admiration. Homer says: Jove paints the rainbow with a purple dye, Alluring man to cast his wandering eye.[43] Others therefore fabled that the bow hath a head like a bull, by which it swallows up rivers.