A very excellent way to render wood incombustible, is to soak it in a strong solution of alum and the sulphate of copper. About one pound of alum and one of the sulphate of copper should be sufficient for 100 gallons of water. These substances are dissolved in a small quantity of hot water, then mixed with the water in the vessel in which the wood is to be steeped. The timber to be rendered fire-proof can be kept under the liquor by stones, or any other mode of sinking it. All that is required is a water-tight vessel, of sufficient dimensions to hold enough of liquor to cover the timber, which should be allowed to steep for about four or five days. After this, it is taken out, and suffered to dry thoroughly before being used.