A convenient apparatus for filtering oil upwards is represented in [fig. 394.] g is an oil cask, in which the impure parts of the oil have accumulated over the bottom. Immediately above this, a pipe a is let in, which communicates with an elevated water cistern n. f is the filter, (placed on the lid of the cask) furnished with two perforated shelves, one at e and another at d; which divide the interior of the filter into three compartments. Into the lower space immediately over the shelf e, the tube b, furnished with a stopcock enters, to establish a communication with the cask; the middle cavity e is filled with coarsely ground charcoal or other filtering materials; and the upper one has an eduction pipe l. When the stopcocks of the tubes a and b are opened, the water passes from the cistern into the oil cask, occupies from its density always the lowest place, and presses the oil upwards, without mixing the two liquids; whereby first the upper and purer portion of the oil is forced through tube b into the filter, and thence out through the pipe l. When the fouler oil follows, it deposits its impurities in the space under the partition c, which may from time to time be drawn off through the stopcock k, while the purer oil is pressed upwards through the filter. In this way the different strata of oil in the cask may be filtered off in succession, and kept separate, if found necessary for sale or use, without running any risk of mixing up the muddy matter with what is clear. According to the height of the water cistern n, will be the pressure, and of course the filtering force. When the filter gets choked with dirt, it may be easily re-charged with fresh materials.
In filtering caustic alkaline lyes through linen or quartz, it is proper to exclude the free contact of air; which is done by inclosing the upper vessel, and attaching a pipe of communication between its cover, and the shoulder of the lower vessel, or recipient of the lyes. In proportion as these flow down, they will displace their bulk of air, and drive it into the top of the upper vessel above the foul lyes.
Many modifications of the above described apparatus are now on sale in this country; but certainly the neatest, most economical, and effective means of transforming the water of a stagnant muddy pool, into that of a crystalline fountain, is afforded by the Royal Patent Filters of George Robins.
FIRE ARMS, Manufacture of. This art is divided into two branches, that of the metallic and of the wooden work. The first includes the barrel, the lock, and the mounting, as also the bayonet and ramrod, with military arms. The second comprises the stock, and in fowling pieces, likewise the ramrod.
1. The Barrel. Its interior is called the bore; its diameter, the calibre; the back end, the breech; the front end, the muzzle; and the closing of the back end, the breech pin or plug. The barrel is generally made of iron. Most military musquets and low-priced guns are fashioned out of a long slip of sheet-iron folded together edge-wise round a skewer into a cylinder, are then lapped over at the seam, and welded at a white heat. The most ductile and tenacious soft iron, free from all blemishes, must be selected for this slip. It is frequently welded at the common forge, but a proper air-furnace answers better, not being so apt to burn it. It should be covered with ashes or cinders. The shape of the bore is given by hammering the cylinder upon a steel mandril, in a groove of the anvil. Six inches of the barrel at either end are left open for forming the breech and the muzzle by a subsequent welding operation; the extremity put into the fire being stopped with clay, to prevent the introduction of cinders. For every length of two inches, there are from two to three welding operations, divided into alternating high and low heats; the latter being intended to correct the defects of the former. The breech and muzzle are not welded upon the mandril, but upon the horn of the anvil; the breech being thicker in the metal, is more highly heated, and is made somewhat wider to save labour to the borer. The barrel is finally hammered in the groove of the anvil without the mandril, during which process it receives a heat every two minutes. In welding, the barrel extends about one-third in length; and for musquets, is eventually left from 3 to 31⁄2 feet long; but for cavalry pistols, only 9 inches.
The best iron plates for gun-barrels are those made of stub iron, that is of old horse-shoe nails welded together, and forged into thin bars, or rather narrow ribands. At one time [damascus] barrels were much in vogue; they were fashioned either as above described, from plates made of bars of iron and steel laid parallel, and welded together, or from ribands of the same damascus stuff coiled into a cylinder at a red heat, and then welded together at the seams. The best modern barrels for fowling pieces are constructed of stub-nail iron in this manner. The slip or fillet is only half an inch broad or sometimes less, and is left thicker at the end which is to form the breech, and thinner at the end which is to form the muzzle, than in the intermediate portion. This fillet being moderately heated to increase its pliancy, is then lapped round the mandril in a spiral direction till a proper length of cylinder is formed; the edges being made to overlap a little in order to give them a better hold in the welding process. The coil being taken off the mandril and again heated, is struck down vertically with its muzzle end upon the anvil, whereby the spiral junctions are made closer and more uniform. It is now welded at several successive heats, hammered by horizontal strokes, called jumping, and brought into proper shape on the mandril. The finer barrels are made of still narrower, stub-iron slips, whence they get the name of wire twist. On the Continent, barrels are made of steel wire, welded together lengthwise, then coiled spirally into a cylinder. Barrels that are to be rifled, require to be made of thicker iron, and that of the very best quality, for they would be spoiled by the least portion of scale upon their inside. Soldiers’ musquets are thickened a little at the muzzle, to give a stout holding to the bayonet.
The barrels thus made are annealed with a gentle heat in a proper furnace, and slowly cooled. They are now ready for the borer, which is an oblong square bit of steel, pressed in its rotation against the barrel, by a slip of wood applied to one of its flat sides, and held in its place by a ring of metal. The boring bench works horizontally, and has a very shaky appearance, in respect at least of the bit. In some cases, however, it has been attempted to work the barrels and bits at an inclination to the horizon of 30°, in order to facilitate the discharge of the borings. The barrel is held in a slot by only one point, to allow it to humour the movements of the borer, which would otherwise be infallibly broken. The bit, as represented in [fig. 395.], has merely its square head inserted into a clamp-chuck of the lathe, and plays freely through the rest of its length.