YOULE’S SHOT-TOWER.
This edifice, which is one of the best of its class, is situated at the foot of Fifty-fourth street, on the East river, in the city of New York. It is hexagonal in form, and rises to the hight of one hundred and seventy-five feet; being sixty feet in diameter at the base, and gradually growing smaller as it rises toward the top. It forms a most striking object of interest; and is remarked by the multitudes who pass by it going up and down the sound, to and from New York. When we consider the small size of the article to the manufacture of which this lofty structure is devoted, the means appear greatly out of proportion with the result. Formerly in casting shot, the apparatus was merely a plate of copper, in the hollow of which were punched a number of holes. This was placed a few feet above a kettle of water, into which the melted lead descended, after passing through the holes in the plate. But in falling so short a distance, and being so suddenly cooled and hardened, the shot did not acquire a perfectly globular form, a desideratum which is now attained by means of shot-towers. In the tower of Mr. McCullough, the largest shot falls from the summit of the tower to the bottom of a well twenty-five feet below the surface of the earth, making the descent one hundred and seventy-five feet. The size of the shot is determined by the size of the holes through which it passes. The furnaces for melting the lead are situated near the top of the tower; three or four tuns of shot are manufactured per day. This method of casting shot was invented by Mr. Watt, the celebrated engineer, in consequence, it is said, of a dream. He tried the experiment from the tower of the church of St. Mary, Radcliffe, and finding it very successful, obtained a patent, which he afterward sold for ten thousand pounds. There are now several shot-towers in the vicinity of London, and different parts of the world; but none more worthy of notice than the one of which we are now speaking. An iron staircase ascends from the base to the summit of the tower. Arsenic is mingled with the lead in proportion of forty pounds to one tun. In casting, the metal is poured through a tube, but descends through the open space of the tower in a continual stream of silvery drops. As the weight of the lead prevents it from scattering or being blown about like water-drops, the workmen pass to and fro, without danger, close by this fiery cascade. The shot is of different sizes, from number one, swan shot, to number twelve, dust shot. Mr. James McCullough has brought the art of the manufacture of the shot to perfection. Certain portions of his factory are kept entirely secret; and the shot manufactured in New York are not surpassed in the world. The cause of most of the imperfections in the manufacture of lead shot, is the too rapid cooling of the spherules by their being dropped too hot into the water, whereby their surfaces form a solid crust, while the interior remains fluid, and in its subsequent concretion shrinks so as to produce the irregularities of the shot. The patent shot-towers originally constructed in England, obviate this evil, by exposing the fused spherules, after they pass through the cullender, to a large body of air during their descent into the water-tub placed on the ground. The greatest erection of this kind is probably at Villach, in Carinthia, being two hundred and forty Vienna, or two hundred and forty-nine English feet high. The following is the process. Melt a tun of soft lead, and sprinkle round the sides of the iron pot about two shovelfuls of wood ashes, taking care to leave the center clear. Then put into the middle about forty pounds of arsenic, to form a rich alloy with the lead. Cover the pot with an iron lid, and lute the joints quickly with loam or mortar, to confine the arsenical vapors, keeping up a moderate fire to maintain the mixture fluid for three or four hours; after which, skim carefully, and run the alloy into ingots or pigs. The composition thus made is in proportion of one pig to one thousand pounds of melted lead. Two or three tons are usually melted at once in large establishments. A crust of oxyd of a white spongy nature, sometimes called cream by the workmen, covers the surface of the lead, which is of use to coat over the bottom of the cullender. The cullenders are hollow hemispheres of sheet-iron, about ten inches in diameter, perforated with holes perfectly round and free from burs. These must be of a uniform size in each cullender; but, of course, a series of different cullenders, with sorted holes for every different size of lead shot, must be prepared. The operation is always carried on with three cullenders at a time, which are supported upon projecting grates of a kind of chafing-dish made of sheet-iron, somewhat like a triangle. This chafing-dish should be placed immediately above the fall; while at the bottom there must be a tub half-filled with water, for receiving the granulated lead. The cullenders are not in contact, but must be parted by burning charcoal, in order to keep the lead constantly at the proper temperature, and to prevent its solidifying in the filter. The hight from which the particles should be let fall, varies likewise with the size of the shot; as the congelation is the more rapid, the smaller they are. The workman then puts the filter stuff into the cullender, pressing it well against the sides; he next gently pours lead into it with an iron ladle. The center of the cullender being less hot, affords larger shot than the sides. Occasionally, also, the three cullenders employed together, may have holes of different sizes; the shot will then be of different magnitudes. These are separated by square sieves of different fineness, and after passing through other minute processes, are ready for sale and use.