METALLURGY. 



579 



peratnre by introducing into the path of the 

 electric current some material affording con- 

 siderable resistance. Coarsely pulverized car- 

 bon was found to be such a material, and to 

 have the further advantage of being the most 

 available substance by the aid of which to 

 effect the reduction of oxides. When this ma- 

 terial, mixed with the oxide to be reduced, was 

 made a part of the electric circuit in a fire- 

 clay retort and submitted to the action of a 

 current from a powerful dynamo-machine, the 

 oxide was reduced, and the temperature was 

 increased to such an extent that the whole in- 

 terior of the retort fused completely. In these 

 experiments, lumps of lime, sand, and corun- 

 dum were fused, with indications of the reduc- 

 tion of the corresponding metals ; and on cool- 

 ing, the lime formed large and well-defined 

 crystals, and the corundum beautiful red, green, 

 and blue octahedral crystals. Further experi- 

 ments discovered that the intense heat thus 

 produced could be utilized for the reduction of 

 oxides in large quantities. It was also found 

 that the fire-brick walls of the furnace would 

 have to be protected from the heat ; and this 

 was done by packing the cone of carbon and ore 

 in pulverized charcoal. In the apparatus now 

 employed by the Messrs. Oowles, a column of 

 fragments of well-calcined charcoal mixed with 

 the ore is imbedded horizontally in finely pul- 

 verized charcoal and covered by a layer of 

 more coarsely broken charcoal, while the whole 

 is placed in a box of fire-brick, covered with 

 perforated tiles and opened at the ends to ad- 

 mit two carbon electrodes an inch and a half 

 in diameter. Through these the current from 

 a dynamo-electric engine of thirty horse-power 

 is made to traverse the central core of ore 

 and carbon. The apparatus also includes a 

 " resistance-box " to protect the machines from 

 the variable resistance within the furnace. 

 With this furnace, aluminum, silicon, boron, 

 manganese, magnesium, sodium, and potassium 

 are reduced from their oxides with ease. In 

 fact, no oxide, it is said, can withstand tem- 

 peratures attainable within it. In September, 

 1885, a small experimental plant, then running 

 with a dynamo of thirty horse-power, was 

 producing daily more than five pounds of 

 aluminum in the form of a rich and brittle 

 alloy, which, by suitable additions of copper, 

 is converted into different grades of aluminum 

 bronze, and these were offered for sale at 

 Cleveland on a basis of five dollars a pound for 

 the contained aluminum. The reduction of 

 silicon is even more easy than that of alumi- 

 num. When silicious sand is mixed with the 

 carbon in the resistance-column, a part of it is 

 fused into a clear glass, and a part is reduced, 

 with the production of a considerable mass 

 of crystallized silicon, a portion of which is 

 revolatilized and reconverted into silica. By 

 adding copper, a hard brittle alloy is formed, 

 containing 6 or 7 per cent, of silicon, from which 

 silicon bronzes can be cheaply made. The di- 

 rect reduction of clay gives an alloy of silicon 



and aluminum, and with copper, a silicon- 

 aluminum bronze which appears to possess 

 exceedingly valuable properties. Boric oxide 

 is rapidly reduced, with evolution of brown 

 fumes, and the formation in presence of copper 

 of a boron bronze. Under certain conditions 

 crystals supposed to be of what is called ada- 

 mantoid boron are formed. In some cases 

 charcoal has been converted into graphite by 

 the action of the furnace. 



A successful method of giving a silver sur- 

 face to iron is employed by a manufacturer in 

 Vienna. His plan is first to cover the iron 

 with mercury, and then to silver by the gal- 

 vanic process. On heating to 300 0., the 

 mercury evaporates and the silver layer is 

 fixed. To save silver, the ware can be first 

 covered with a layer of tin. Ware thus cov- 

 ered with tin chemically pure, and silvered, is 

 said to be much less costly than any other sil- 

 vered metal. 



The New Haven (Conn.) Wire Company has 

 exhibited a wire galvanized by a new process, 

 in which, it is claimed, by means of a thorough 

 union of the coating with the body of the wire, 

 scaling is prevented, and a smooth, firm sur- 

 face is secured under all circumstances. Soft- 

 ness and tensile strength and uniformity of 

 temper ard said to be obtained to an extraordi- 

 nary degree. One of the features of the pro- 

 cess is the use of a diminished quantity of acid. 



A simple method of bending cast-iron with- 

 out danger of fracture has been found to be by 

 the judicious application of heat, the degree of 

 which may not be very high, with moderate 

 pressure. The heads of leaders or spoolers in 

 a cotton-mill were given a decided curvature 

 by heating the straight casting in the flame of 

 an alcohol-lamp. After the under side of the 

 casting had been heated to a degree that would 

 have drawn hardened steel to a straw-color, a 

 pressure by weighted lever was introduced 

 upon the upper side. As the lamp was moved 

 from point to point, it was surprising to see 

 how the iron yielded to the pressure and the 

 heat. A crooked casting was likewise straight- 

 ened by the careful use of two gas-flames dif- 

 fused by wire-netting, and of weight suitably 

 applied. 



Apparatus. Mr. James Riley has been experi- 

 menting with a cupola-furnace, which he has 

 devised to aid in shortening the duration of 

 the operations for making open-hearth steel. 

 His aim was to reduce the time required for 

 charging the furnace, and this he sought to 

 accomplish by having the metal to be charged 

 ready, in the fluid state, to be run directly into 

 the furnace. The result of his efforts is the 

 construction of a cupola- furnace, in which gas- 

 eous is substituted for solid fuel, the gas-gen- 

 erator being dependent for its operation upon 

 a forced blast obtained from an ordinary 

 blower, while the air for supporting combus- 

 tion in the body of the furnace is also ob- 

 tained from the blower. From the prelimi- 

 nary experiments he has performed, with 



