SMELTING ORES BY ELECTRICITY 



bolted to a bottom plate of cast iron 48 inches in diameter. 

 The casing was made in two cylindrical sections to facilitate 

 repairs. To render the inductance as small as possible, the 

 lines of magnetic force in the iron case were prevented from 

 closing by the replacement of a vertical strip of 10 inch 

 width of the casing by a copper plate. Carbon paste was 

 rammed in the bottom of the furnace up to the lower part 

 of the crucible. The lining consisted of common firebrick, 

 which from the bottom of the crucible up for a distance a 

 little above the slag level, was covered with carbon paste to 

 a thickness of a few inches. The lining of tlie furnace was 

 made the shape of two cones, set base to base, having 

 dimensions as follows : 



Dimensions at bottom of crucible, 24 inches. 



'* at widest part, - - 32 " 



" at top of furnace, ' - 30 " 



Length, 44 " 



The electrode was a square prism 16 in. x 16 in. by 6 

 feet long, The contact with the cables carrying the elec- 

 tric current to the electrode consisted of a steel shoe riveted 

 to four copper plates, which ended in a support for a 

 pulley. The electrode, with its contact, was supported by 

 a chain passing under the pulley, one end of the chain 

 being fastened to the wall, the other end passing over a 

 winch operated by a worm and worm wheel. This formed 

 a convenient arrangement for regulating the electrode by 

 hand. The energy was furnished by one phase of a three* 

 phase 400 K.W. 30'Cycle 2,400 volt A.C. generator belted 

 to a 300 H.P. 50c volt D. C. motor. A current at 2,200 

 volts was delivered to the primary of an O.I.S.C. trans- 

 former of 225 K.W., and .stepped down to 50 volts. This 

 transformer was placed in a room adjoining the furnace 

 room. The current of approximately 5,000 amperes at 50 

 volts was delivered to the furnace. The instruments used 

 were a voltrneter, armeter, power factor meter, and record- 



