_Nomenclature of Screws._—In all the screws, the parts are the stem, the head, the slot and the thread. CHAPTER XXX. ON BROWNING. _Object of Browning._—Browning is done for the purpose of subduing the bright color of the barrel from the sight of game; to bring out the fibres of the metal to show their form and beauty, and also to show whether the metal be free from flaws. It does not prevent barrels from rusting, but rust will not attack so readily as if left in a bright condition. The browning is very certain to make all defects appear, except those designedly hidden, and not only defects of materials but the filing and finishing of the barrel, if not well done, will appear in marks in certain lights. A thoroughly well-filed barrel presents, what may be called, a deep liquid appearance. _Preparatory Process._—The process of browning is simple and cheap, and at the same time serves to protect a gun, in some measure, from rust, and also adds to its appearance. The operation consists in producing a very thin uniform film of rust, or oxide, upon the iron and giving a gloss to its surface by rubbing wax over it, or by coating it with some kind of varnish, as shellac varnish. Preparatory to browning, the barrel having been filed and polished bright, is rubbed with lime to remove all grease. Some gun makers use wet lime or lime water and then rub in dry powdered lime. The vent holes are to be stopped with wax or wooden plugs, and both breech and muzzle are to be plugged with wooden rods which serve as handles to hold the barrel during the operation. The object of plugging is to prevent the mixture from finding its way into the interior of the barrel and the breech and muzzle plugs also serving as handles, prevent the hands from coming in contact with the barrel, which would prevent the stain from “taking,” and consequently cause a spot of different color from that on other portions of the work. The solution is generally applied with a sponge or cloth, sponge being preferable, until the surface is equally moistened, and after standing in a warm place, generally about twenty-four hours, it is rubbed off with a stiff brush or a wire card. The state of the atmosphere will have much to do with the action of the browning mixture. It can be easily ascertained when the barrels are dry enough to work, as by applying the card, if dry, the rust will fly off quickly, but if not dry, the rust will adhere firmly and the surface of the barrel will look streaky. Some mixtures will dry in twelve hours or even less, but twenty-four hours will insure their being perfectly dry. The process of wetting and brushing, or “carding,” is repeated until the barrel has acquired the desired color. When this stage is reached the barrel is freely washed with hot water, in which a little potash may be mixed. Then wash with clean water and dry thoroughly. A little lime water may be used as a wash to destroy any free acid that may remain in the pores of the metal.