the reduction of Oxides of Silicon, Aluminum, etc. 309 



short time since Eugene H. Cowles and Alfred H. Cowles, of 

 Cleveland, conceived the idea of obtaining a continuous high 

 temperature on an extended scale by introducing into the path 

 of an electric current some material that would afford the 

 requisite resistance, thereby producing a corresponding increase 

 in the temperature. After numerous experiments that need 

 not be described in detail, coarsely pulverized carbon was se- 

 lected as the best means for maintaining a variable resistance, 

 and, at the same time, as the most available substance for the 

 reduction of oxides. When this material, 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 pow- 

 erful dynamo machine, not only was the reduction accomplished, 

 but the temperature increased to such an extent that the whole 

 interior of the retort fused completely. In other experiments, 

 lumps of lime, sand and corundum were fused, with indica- 

 tions of a reduction of the corresponding metal ; on cooling, 

 the lime formed large well defined crystals, the corundum 

 beautiful red, green and blue hexagonal crystals. 



Following up these results with the assistance of Charles F. 

 Mabery, Professor of Chemistry in the Case School of Applied 

 Science, who became interested at this stage of the experiments, 

 it was soon found that the intense heat thus produced could be 

 utilized for the reduction of oxides in large quantities, and ex- 

 periments were next tried on a large scale with a current from 

 two dynamos driven by an equivalent of fifty horse-power. 

 For the protection of the walls of the furnace, which were 

 made of fire-brick, a mixture of the ore and coarsely pulver- 

 ized gas carbon was made a central core, and it was surrounded 

 on the sides and bottom by fine charcoal, the current follow- 

 ing the lesser resistance of the central core from carbon elec- 

 trodes which were inserted at the ends of the furnace in contact 

 with the core. In order to protect the machines from the vari- 

 able resistance within the furnace, a resistance box consisting 

 of a coil of German silver wire placed in a large tank of water 

 was introduced into the main circuit, and a Brush ammeter 

 was also attached by means of a shunt circuit to indicate the 

 quantity of current that was absorbed in the furnace. The 

 latter was charged by first filling it with charcoal, making a 

 trough in the center and then filling this central space with 

 the ore mixture, which was covered with a layer of coarse char- 

 coal. The furnace was closed at the top with fire-brick slabs 

 containing two or three holes for the escape of the gaseous pro- 

 ducts of the reduction, and the entire furnace made air-tight by 

 luting with fire-clay. Within a few minutes after starting the 

 dynamo, a stream of carbonic oxide issued through the open- 

 ings, burning usually with a flame eighteen inches in height. 



