Elliptical cupola furnaces, provided with sectional cast-iron jackets, forming a bosh 29 in. high immediately above the tuyere level, are used for treating the slags resulting from the fusion of the " mineral" of Lake Superior in reverberatory furnaces. In these cupola., in place of distinct. tuyere-openings, a Fin. slot encircles the entire furnace, just below the water-bosh. Below the tuyeres is a crucible 34 in. deep, nearly the full size of the furnace, closed by a drop-bottom. The water-bosh, which is 22 in. high, consists of curved sections of cast iron, fitted closely together. The cupola is 7 ft. 6 in. high, from tuyeres to charging door, and has a major axis of 7 ft. and a minor axis of 4 ft. 9 in.
Reverberatory Furnaces are constructed of very varied forms and dimensions, but the prin ciples of all are the same. They consist of two main portions—the fireplace (either an ordi nary grate or a gas-producer) and the laboratory part, the fuel being separated from the ore, or the materials to be heated, by means of a fire-bridge, which is simply a wall of refractory brick, usually furnished with an air-channel to keep it cool. The flames draw over this bridge and reverberate into the laboratory part, which is connected by means of a flue with the chimney, which serves for the withdrawal of the consumed gases and the production of draft. The reverberatory slagging-furnace used in lead-smelting is a modification of the re verberatory roasting-furnace (sec FURNACES, ROASTING). It has two hearths, one a step higher than the other, the lower hearth being next the fire-bridge. The raw ore, having been fed in at the flue end of the furnace, is gradually worked forward, being desulphurized on the way, and is finally pushed down to the lower hearth, where the heat is more intense, and the ore is fused or agglomerated, thus preparing it for the blast-furnaces. This practice is not pursued every where, in many places it being the custom to feed the roasted ore to the blast-furnaces with out slagging. At Denver and Pueblo, Col., however, the tendency seems to be distinctly in favor of the preliminary slagging.
Reverberatory furnaces for copper-smelting are in general use in Swansea, and the method is, in fact, distinctly Welsh. In certain copper regions of the United States, also, furnaces of this class are exclusively used. The American reverberatories are modeled closely after those of Wales, which have been in use for many years, the only improvements having been in their size, which there is a constant tendency to increase, with the consequent gain in capacity. The hearth of the copper-reverberatory is usually an elongated oval, the exterior shape of the furnace being rectangular, however. In an ordinary furnace the hearth is about 15 ft. lung and 10 ft. wide, the capacity of a furnace of this size being about 16 tons per 24 hours. At
the works of the Boston & Colorado Smelting Co., at Argo, Col., Mr. Richard Pearce has introduced furnaces with hearths 24 X 14 ft., thereby increasing the capacity to over 28 tons per 24 hours.
Within the past ten years an important improvement has been made in copper-smelting by the introduction by Si. Man hes of a system of Bessemerizing copper matte, and the process is now being quite extensively used. The improved Mantles converter, such as is used at the .ierez-Lanteira smelting works in Spain, is shown in Figs. 3 and 4, of which the former represents a transverse section of the converter, and the latter a side elevation of the converter and its carriage. The appa ratus consists of an iron cylinder 4 ft. 3 in. in length, having an outer diameter of 4 ft. 2 in. It is made of iron plates thick. In the upper part of the cylinder there is an opening on which a conical chimney is riveted, the highest part of which has a diameter of 22 in. On one side of the cylinder, and all along its length, an air-chamber. C, is fixed, of rectan gular shape, and in this 11 tuyeres, 7' T, of i in. diameter are inserted. In front of each tuyere there is a hole made in the outside of the air reservoir, which is closed by a wooden stopper. Through these holes the tuyeres are kept free for the entrance of the air. At one of the ends of the air reservoir tubes, A, are fixed for the entrance of the blast, and these tubes are so arranged that, the highest being connected with the air main, whatever position the converter takes on turning on its axis, the supply of air is kept up un interruptedly. On the outside of the converter, and at half of its length, a toothed segment. E, is placed, for the purpose of moving the converter on its axis in the manner to be described hereafter. On both sides of this toothed segment. and about 12 in. from the end of the con verter, two Ihit ribs of iron are placed. Lastly, in the upper part of the converter two strong Books are provided to lilt it by means of a crane or differential pulley-block whenever required. The carriage which supports the converter runs on rails. and each wheel has fastened to it a toothed wheel which gear: into a small pinion. By means of the handles, .,1/, the wheels are turned, giving to the carriage a smooth forward or backward movement. On the carriage there are four loose wheel=, R. on which the converter rests, and which facilitate the movement of the converter round its axis. For the purpose of complete ualive rcent the carriage carries a shaft, in the center of which is a worm-wheel geared to the tooth segment, IL The shaft, when operated by the handle. 13/, places the converter in the inclined position suitable for loading, unloading, blowing, or discharging the slag as it may lie required.