They also call the air, when it is without light κνέφας, as being as it were κενὸν φάους (_void of light_.) The air collected and condensed into a cloud is called νέφος, from its negation of light (νή-φάος). The words also ἀχλύς and ὁμίχλη (_mist_), and whatever else restrains the perception of light from the sense, are but distinctions of the air; insomuch that the same part of it which is invisible and without color (ἀειδές and ἄχρωστον) is called Hades and Acheron. So that, as the air grows dark when the splendor of it fails, in like manner when heat fails, that which is left is no more than cold air, which by reason of its coldness is called Tartarus. And this Hesiod makes manifest, when he calls it Τάρταρον ἠερόεντα (or _cloudy Tartarus_); and when a man quakes and shivers for cold, he is said to tartarize. And so much for this. 10. But in regard corruption is the alteration of those things that are corrupted into that which is contrary to every one of them, let us consider whether it be a true saying, “The death of fire is the generation of air.” For fire dies like a living creature, being quenched by force or going out of its own accord. Now quenching makes the alteration of it into air more conspicuous. For smoke is a sort of air, or, according to Pindar, a fuliginous vapor and exhalation, “lashing the air with steaming smoke.”[121] On the other side, when fire goes out for want of fuel, as in candles, you shall observe a thick and cloudy air ascending from the top of them. Moreover, the vapor steaming from our bodies upon the pouring of cold water after hot bathing or sweating sufficiently declares the alteration of extinguished heat into air, as being naturally opposite to air; whence it follows that the air was at first dark and cold. 11. Then again, congelation, which is the most forcible and violent of all things that befall our bodies by reason of cold, is the affection of water, but the action of air. For water of itself is easily diffused, loose in its parts, and not readily congealed together; but it is thickened and compressed by the air, by reason of the coldness of it. Which is the reason of the proverb: But if the southern wind provoke the north, Snow straight will cover all the earth. For the southern wind preparing the moisture as matter, presently the north wind receives and congeals it. And this is manifest from the consideration of snow; for ere it falls, you shall observe a thin and sharp cold air breathing before it. Aristotle also tells us, that whetstones of lead [?] will melt and run in the winter through excess of freezing cold, merely upon the setting of the water near them. For it is probable that the air compresses and gripes the bodies so close together, that at length it breaks and crumbles them in pieces.