But who can explain the strange properties of fire itself, which blackens everything it burns, though itself bright; and which, though of the most beautiful colours, discolours almost all it touches and feeds upon, and turns blazing fuel into grimy cinders? Still this is not laid down as an absolutely uniform law; for, on the contrary, stones baked in glowing fire themselves also glow, and though the fire be rather of a red hue, and they white, yet white is congruous with light, and black with darkness. Thus, though the fire burns the wood in calcining the stones, these contrary effects do not result from the contrariety of the materials. For though wood and stone differ, they are not contraries, like black and white, the one of which colours is produced in the stones, while the other is produced in the wood by the same action of fire, which imparts its own brightness to the former, while it begrimes the latter, and which could have no effect on the one were it not fed by the other. Then what wonderful properties do we find in charcoal, which is so brittle that a light tap breaks it and a slight pressure pulverizes it, and yet is so strong that no moisture rots it, nor any time causes it to decay. So enduring is it, that it is customary in laying down landmarks to put charcoal underneath them, so that if, after the longest interval, any one raises an action, and pleads that there is no boundary stone, he may be convicted by the charcoal below. What then has enabled it to last so long without rotting, though buried in the damp earth in which [its original] wood rots, except this same fire which consumes all things?