1 oz. sweet nitre. 1/2 oz. tincture of steel. 1/4 oz. blue vitriol. 6 drops nitric acid. 14 grs. corrosive sublimate. 1 pint of water. When the barrels are dark enough, drop a few drops of muriatic acid in a basin of water, and wash the barrel slightly, to brighten the twists. This last process is borrowed from the Belgians. In the working of their extremely fine Damascus barrels, they found a very great difficulty in staining them so as to produce a clear and distinct figure. The way they now proceed is either to eat away the particles of iron, leaving the steel prominent and the barrels bright; or they polish them extremely fine from end to end, and then blue them in a stove with charcoal. The process is thus described in the notes to a German translation, by Dr. Schmidt, of Weimar, of my last edition of the “Science of Gunnery.” “The method of browning the Damascus barrels, which are so much admired in England for their distinctness in colour and beauty of figure, is obtained very simply: namely, first burnish the barrels very fine; then cover them with bone oil; pound, or drop, or strew wood-ashes all over; then heat them in a cage of wire filled with charcoal, until you obtain a dark first blue; after they are cold, mix a small quantity of sulphuric acid in water (a quarter of a pint with so many drops); then take a hard brush and apply it to the barrel, when the acid will extract the colour from the steel, leaving the iron with its greater adhesion covered with the blue colour. Great care must be used and skill displayed to keep a good colour and not to extract too much.” This we cannot do, because we solder with tin. The “Belgian Damascus” barrels are generally “eat up,” as it is technically termed. “Pickled” is the term also used to describe the process, which is simply eating away the softer metals from around the steel or harder material. The best preparation for this purpose is 1 lb. of the sulphate of copper (known as blue vitriol) dissolved in a gallon of soft water, at the boiling point, and continued boiling in an earthenware vessel, until the quantity is reduced by evaporation 25 per cent.; let it cool, and then pour it into a leaden trough or bath. The barrels, when properly secured at the muzzle and breech-ends to prevent the liquid getting into the interior, are immersed therein. The solution will act sufficiently upon the metals in the space of from fifteen to twenty minutes; care being taken to remove and carefully wash them with cold water, and then, after observing the progress of the _pickling_, re-immersing them as before, until the operation is complete. Then pour boiling water over them, and scratch them well with a steel brush, which will eventually give that beautiful bright “wavy” surface much admired by many people. Laminated steel barrels also look very well, after being subjected to this operation.