The rolling, forging, and swaging rooms are all connected, and form, as it were, one extended apartment.  In this are placed hundreds of forges, furnaces, trip-hammers, rolling-mills, dropping-machines, and trimming-machines,—­besides scores of sledge-hammers, wielded by stalwart arms.  The noise here is so great that no effort of the voice avails to make itself heard, and I doubt if even the loudest thunder would make any appreciable addition to the general clangor.  Small iron carts, filled with hot iron, are incessantly whirling around you; red-hot sparks, or melting drops of iron, are flying about the room in all directions; the air is hot to suffocation, and sulphurous from the burning of bituminous coal; while hundreds of swarthy faces, begrimed with grease and dirt, are dripping with sweat:  so that you can scarce avoid the suspicion that you have at last stumbled into the infernal regions, and are constantly wondering why some of Pluto’s imps do not seize you and plunge you into some horrible furnace, or chop you up under a trip-hammer.

Having survived the examination of this department, you follow your guide from the forging-room down a winding flight of iron steps to the water-wheels, which are situated forty feet under ground.  These wheels are so arranged that they can be run together or separately; they are generally run together, and in connection with the immense low-pressure engine.

After the barrels are bored, turned, milled, and straightened, they are next to be polished.  For this purpose they are placed in upright frames, each frame containing five barrels.  The polishing is done by means of hard, wooden rubbers, provided with a plentiful supply of lard-oil and emery.  The rubbers are placed horizontally, with their grooved ends pressing by means of springs against the barrels, which are drawn between them by a very regular and rapid vertical motion.  The barrels are also turned around slowly and continuously by a lateral movement, which insures a uniform polish.  They are allowed to remain in the first polishing-machines fifteen minutes, and are then placed in a similar machine and go through a second polishing, differing from the first simply in the absence of the pulverized emery,—­oil only being used upon the rubbers during this finishing operation.  The musket is now completed, with the exception of the rifling, and some slight polishing to be done by hand at the muzzle and breech.

Two polishing-machines are used for ramrods, similar in construction to those above described,—­ten rods being polished at once.  The bayonet is polished upon emery-wheels.  These wheels are made of wood bound with leather, upon which there is placed a sizing composed of glue and pulverized emery.  The polishing by this process is very rapid.