_To Work Brass._—This material is a combination of copper and zinc, and since zinc is not so malleable as copper, it renders the brass less malleable. Nevertheless it forges out pretty well under the hammer, in a cold state, the only condition in which it can be so worked. Hammering increases its hardness with great rapidity, soon converting it into a very fair spring metal. Brass springs are quite common—they are all made by repeatedly hammering or rolling the metal while cold. As in the case of both silver and copper, heating and gradual cooling removes this hardness. This is the plan for softening usually recommended in books on working metals, but no advantage will be found to arise from the gradual cooling in the case of either silver, copper or brass. The custom is to heat the metal to the lowest degree that would show redness and then plunge it directly into cold water. _To Cast Brass._—The gunsmith may occasionally find it necessary to cast something in brass. This he can do without trouble, as brass melts quite easily. The mould should have vents at or near the top to admit the free escape of air as the molten metal runs in to take its place; and it is always best, if possible, to arrange so that the metal will enter the mould near the bottom and rise up in the filling. Without such an arrangement there is danger of air bubbles remaining under the metal and spoiling the casting. The metal should be heated only to a degree high enough to admit of flowing freely and no higher. _To Brass Iron._—Clean and polish the iron thoroughly, being extremely careful not to touch its surface with the fingers at the finishing; then plunge it into molten brass. Take out immediately; a thin coating of brass will be found covering the iron, which may be polished or burnished, giving the article the appearance of solid brass. _To Clean Brass._—To half a pint of soft water add one tablespoonful of oxalic acid. Wash the article with this, then cover with prepared chalk, brush dry and polish with chamois skin, as in cleaning silver. The solution may be bottled and kept on hand for use as wanted.