Thus, by putting two or more billets of wood together, by rapid friction you produce fire.

Abstract the air suddenly, and your fire becomes extinct; abstract the wood, and you have the same result.

From these two experiments it is shown that fire has no independent existence, and therefore is not an element.

On the other hand, take a billet of wood and let it be completely saturated with water; the wood acquires a new property (as also by the application of fire, which converts it into ashes and air), for its specific gravity is increased, it becomes less inflammable, emits vapor more readily, and yields less readily to the blow of the axe.

Place the same billet under a powerful screw, and a vessel beneath.