Plutarch De primo frigido 19

[19] In view of these considerations, regard the facts in the following light: every force, presumably, whenever it prevails, by a law of nature changes and turns into itself whatever it overcomes. What is mastered by heat is reduced to flames, what is mastered by wind turns to air; and anything that falls into the water, unless it gets out quickly, dissolves and liquefies. It follows, then, that whatever is completely frozen must turn into primordial cold. Now freezing is extreme refrigeration that terminates in a complete alteration and petrifaction when, since the cold has obtained complete mastery, the moist elements are frozen solid and the heat is squeezed out. This is the reason why the earth at its bottommost point is practically all solid frost and ice. For there undiluted and unmitigated cold abides at bay, thrust back to the point farthest removed from the flaming aether. ¹ As for these features that are visible, cliffs and crags and rocks, Empedocles ² thinks that they have been fixed in place and are upheld by resting on the fire that burns in the depths of the earth; but the indications are rather that all these things from which the heat was squeezed out and evaporated were completely frozen by the cold; and for this reason they are called pagoi. ³ So also the peaks ⁴ of many of them have a black crust where the heat has been expelled and have the appearance of debris from a conflagration. For the cold freezes substances to a varying degree, but hardest those of which it is naturally a primary constituent. Thus, if it is the nature of heat to lighten, the lightest object will have most heat, and if it is the nature of humidity to soften, the softest will have the most humidity; so, if it is also true that the nature of cold is to harden, then it must also follow that the hardest object will have the most cold - that is to say, just as the earth has. But what is coldest by nature is surely also primarily cold, so that the earth is in fact cold both primordially and naturally; and, of course, this is obvious even to the senses. Mud, in fact, is a colder thing than water; and men extinguish a fire by dumping earth upon it. Blacksmiths, when their iron becomes fiery and begins to melt, sprinkle on it marble chips and gypsum to check and cool it off before it melts too much. It is also true that dust cools the bodies of athletes and dries up their sweat.