_Browning Inferior Barrels._—Inferior quality of Birmingham barrels are browned as follows: Dissolve as much muriate of mercury as can be taken up in a glassfull of alcohol. Mix this solution in one pint or more of water. A small quantity of this mixture is poured on a little whitening and laid on the barrel with a sponge, rather lightly. As soon as dry, brush off and lay on a fresh coating. So proceed until the barrel is dark enough, which is generally about two or three days. The effect is to make the softer portions of the metal a beautiful brown, while the harder portions remain quite light. The rusting process is killed by washing in hot water, after which the barrels are suddenly immersed in cold water. This has the effect of heightening the brightness of both colors. _Plain Welded Barrels made to Resemble Twist._—Plain welded barrels are made to resemble twist barrels by wetting a thread or fine cord with dilute acid, and winding it around the barrel so as to make spiral lines, running all along its surface. Wherever the thread touches a slight coating of rust will be formed. The barrel may be treated in this way two or three times, and the spiral windings of the thread will exhibit fine dark lines closely resembling twist barrels. To wind the thread the barrel may be put between the centres of a lathe, and so turned while it winds the thread upon it, being guided by the hand, or the barrel may be supported between centres or put on a rod of wood, which may be turned by a crank or handle. Barrels may be colored by exposing them to a degree of heat sufficient to produce a blue tinge, and is done to color pistol barrels, but when double gun barrels are soft-soldered together this cannot be done on account of danger of melting the solder. The inner surface of the barrel, which is also so colored, must be polished after the operation.