Page:The American Cyclopædia (1879) Volume II.djvu/762

 742 BLOOMAEY formerly much used, us well as in the neighbor- ing parts of France, especially in the depart- ment of Ariege. The Catalan forge as used in France consists of a rectangular hearth con- structed chiefly of heavy iron plates, and in the largest size measures 40 by 32 inches, and is from 20 to 24 inches deep, or from 12 to 15 in- ches below the tuyere or pipe through which the blast enters. In some cases, however, fur- naces of not more than one half these dimen- sions are built. The pressure of the blast does not exceed 1^ or If inch of mercury, and the tuyere is directed downward at an angle of 30 or 40. The wall facing the tuyere slopes out- ward toward the top, and in working the greater part of the charge of ore is heaped against it, and occupies from one third to one half of the cavity of the furnace, the remaining space being filled with ignited charcoal. The ore is previously broken so that the largest lumps are not more than two inches in diame- ter, while from one third to one half of the material will pass through a screen the bars of which are four tenths of an inch apart. This finer ore is thrown on the surface of the fire from time to time during the operation, which is conducted with many precautions as to regu- lating the blast, stirring, and supplying the fine ore and coal. At the end of six hours, in the ordinary routine, there is withdrawn from the bottom of the furnace an agglomerated mass of reduced but unmelted iron, which is then forg- ed into blooms or bars. The operation con- sumes, in one of the larger-sized forges, about 9J cwt. of iron ore (a limonite holding 40 or 50 per cent, of iron is treated in the Arie'ge) and 10 cwt. of charcoal, and yields 3 cwt. of bar iron. According to another calculation, there are required in this process, for the production of 100 Ibs. of iron, 340 Ibs. of charcoal and 312 Ibs. of an ore containing from 45 to 48 per cent, of iron. Of this about seven tenths are ob- tained in the metallic state, the remainder passing into the slag; 100 Ibs. of the ore yield 81 Ibs. of bar iron and 41 Ibs. of slag, which is a dark-colored basic silicate, very rich in oxide of iron. It is to be remarked that in this direct method of treatment a portion of the oxide of iron is always consumed in fluxing the impurities of the ore, so that the purest ores are generally sought for the purpose. In the blast furnace, on the contrary, by the judicious use of lime or other basic fluxes, the slags are obtained almost free from iron, and the loss of the metal is thus avoided. The German bloom- ary furnace was formerly used in Silesia and the Palatinate, and is described at some length by Karsten (1816), but is dismissed with a few words in Bruno KerPs treatise (Huttenkunde, 1864, iii. 427), from which its use would seem to be nearly or quite abandoned in Germany. According to Karsten, the German bloomary consists of an iron pot, or a box of iron plates, in either case lined with refractory bricks, and having an internal diameter of from 14 to 21 inches, and the same depth, the dimensions varying with the fusibility of the ore, the force of the blast, and the quality of the coal. The tuyere is horizontal. The furnace having been filled and heaped up with burning charcoal, the ore is thrown upon the fire by shovelfuls at a time, until a loup of sufficient size has been formed at the bottom of the hearth, as already described in the Catalan method. When the blast is too intense, or the coal very dense, it may happen that the reduced iron becomes carburetted by the excessive heat to such an extent as to produce a steel-like iron, or even molten cast iron, instead of a loup of soft mal- leable iron. A similar state of things some- times occurs in the Catalan forge, and is occa- sionally taken advantage of to produce an imperfect kind of steel. From the above de- scription it will be seen that the method by the German bloomary differs from that by the Catalan in the fact that in the latter the greater part of the charge of ore is placed at the com- mencement of the operation, in a coarsely broken state, on the sloping wall of the fur- nace, opposite the tuyere, while the remaining portion is subsequently projected in a more finely divided condition upon the surface of the fire. In the German method, on the contrary, the whole of the ore is reduced to this finer condition, and is added by small portions; a plan which dispenses with the charging of the furnace with ore after each operation, as in the Catalan method, and permits of a continuous working, interrupted only by the withdrawal of the loups from time to time. The German bloomary in an improved form is extensively used for the reduction of iron ores in the United States, where it is known by the name of the bloomary fire, the Jersey forge, or the Cham- plain forge ; it is also frequently called the Cata- lan forge, from which, as already shown, it is dis- tinct in form and still more distinct in the man- ner in which it is worked. This latter seems however to be unknown, at least in the north- ern and eastern portions of the United States. i The German bloomary was probably introduced into North America early in the last century. Among the forges in operation in New Jersey and Pennsylvania in 1856, Lesley, in his "Iron Manufacturers' Guide," mentions one as having been established in 1733 and another in 1725. The magnetic iron sands of the seacoast early attracted the attention both of the American colonists and of metallurgists in England, as appears from the experiments of Dr. Mohlen as early as 1742 upon what was called the Vir- ginian black sand (the name of Virginia being at a still earlier period given to the whole coast from Canada to Florida). These black sands from Killingworth, Connecticut, were there successfully treated in a bloomary fur- nace in 1762 by the Rev. Jared Elliot, who obtained blooms of 50 Ibs. weight of iron, which was afterward made into steel of supe- rior quality, and for his discovery received the following year a medal from the society of arts of London. Steel works had at that time been