Now it must not be regarded as settled that the facts are as we have just said; we have merely tried to bring together and compare various opinions in order to determine what seems most reasonable. For we see that all fire originates in force. If a hard stone is stricken against hard iron, fire comes out of the iron and out of the energy of the stroke when they clash. You can also rub pieces of wood against each other in such a way that their antagonism will produce fire. It also happens frequently that two winds rising at the same time will go against each other; and when they meet in the air, heavy blows fall, and these blows give forth a great fire which spreads widely over the sky.[216] At times it also happens that this fire is driven to the earth where it causes much damage by burning houses and sometimes forests and ships at sea. But all the fires that I have now named, whether they come from iron, or winds colliding in the air, or any of those mighty forces which can produce fire, will consume trees, forests, and earth: while the fire which we discussed earlier and which appears in Iceland refuses all these things, as I have already shown. Now these facts lead to this conclusion as to its nature, that it is more likely to have arisen from dead things or from like sources, than those other fires that we have now discussed. And in case it is as we have imagined, it is likely that the great earthquakes of that country originate in the power of those mighty fires that well through the bowels of the land. Footnote 216: The common belief of medieval scientists was that lightning was caused by the collision of clouds. ------------------------------------------------------------------------ XIV THE VOLCANIC FIRES OF ICELAND _Son._ I should like very much, with your permission, to ask further about this fire. You stated earlier in your remarks that Gregory has written in his _Dialogues_ that there are places of torment in Sicily; but to me it seems more likely that those places are in Iceland. You also said that so vast are the fires in the bowels of the land that earthquakes arise out of their violent movements; but if the fires are so destructive to stone and rock that it melts them like wax and feeds wholly upon them, I should imagine that it would soon consume all the foundations beneath the land and all the mountains as well. Though you may think I am asking childish questions about these things, still I entreat you to give indulgent replies; for, of course, one can ask many questions that reveal youth rather than wisdom.