Plutarch, De primo frigido
Goodwin, Ed.

This being obvious to sight, let us consider the effect. Every faculty, wherever it prevails, changes into itself whatever it overcomes. Thus whatever is overcome by heat is set on fire; that which is vanquished by wind is changed into air. That which falls into water becomes well moistened, unless quickly saved. Of necessity, therefore, those things which are violently affected by cold must be changed into the primitive cold. For freezing is an excess of refrigeration; which congelation ends in alteration and petrifaction, when the cold, prevailing every way, congeals the liquid substance and presses forth the heat; so that the bottom of the earth is, as it were, a kind of congelation, and altogether ice. For there the cold inhabits simple and unmixed, and removed hard and rigid at [p. 327] the greatest distance from the sky. But as for those things which are conspicuous, as rocks and precipices, Empedocles believes them to be thrust forth and supported by the fire that burns in the bottom of the earth. Which appears the more, in regard that, wherever the heat is pressed forth and vanishes away, all those things are congealed or stiffened by the cold; and therefore congelations are called πάγοι (stiffened). And the extremities of many things where heat fails, growing black, make them look like brands when the fire is out. For cold congeals some things more, some things less; more especially such things wherein it is primitively existent. For as, if it be the nature of hot to render light, that which is hottest is lightest; if of moist to soften, that which is moistest is softest; so if it be the nature of cold to congeal, of necessity that which is coldest must be most congealed,—that is to say the earth,—and that which is most cold must be that which is by nature and primitively cold, which is no more than what is apparent to sense. For mud is colder than water, and earth being thrown upon fire puts it out. Your smiths also, when their iron is melted and red hot, strew upon it the dust of marble to cool it and stop the running of it too fluidly. Dust also cools the bodies of the wrestlers, and dries up their sweat.