224 THE SCIENTIFIC PAPERS OF 



description upon its iron core, the abscissas representing the depth 

 of immersion of the uppermost end of the iron in the coil in 

 centimetres, and the ordinates the attractive force in grams. 



This automatic adjustment of the arc is of great importance to 

 the attainment of advantageous results in the process of electric 

 fusion ; without it the resistance of the arc would rapidly diminish 

 with increase of temperature of the heated atmosphere within the 

 crucible, and heat would be developed in the dynamo-electric 

 machine to the prejudice of the electric furnace. The sudden 

 sinking or change in electrical resistance of the material under- 

 going fusion would, on the other hand, cause sudden increase in 

 the resistance of the arc, with a likelihood of its extinction, if such 

 self-adjusting action did not take place. 



Another important element of success in electric fusion consists 

 in constituting the material to be fused the positive pole of the 

 electric arc. It is well known that it is at the positive pole that 

 the heat is principally developed, and fusion of the material con- 

 stituting the positive pole takes place even before the crucible 

 itself is heated up to the same degree. This principle of action 

 is of course applicable only to the melting of metals and other 

 electrical conductors, such as metallic oxides, which constitute the 

 materials generally operated upon in metallurgical processes. In 

 operating upon non-conductive earth or upon gases, it becomes 

 necessaiy to provide a non-destructible positive pole, such as 

 platinum or iridium, which may, however, undergo fusion, and 

 form a little pool at the bottom of the crucibL. 



In this electrical furnace some time, of course, is occupied to 

 bring the temperature of the crucible itself up to a considerable 

 degree, but it is surprising how rapidly an accumulation of heat 

 takes place. In working with the modified medium-sized dynamo 

 machine, capable of producing 3G webers of current with an ex- 

 penditure of 4 horse-power, and which, if used for illuminating 

 purposes, produces a light equal to G,000 candles, I find that a 

 crucible of about 20 centimetres in depth, immersed in a non- 

 conductive material, is raised up to a white heat in less than 

 a quarter of an hour, and the fusion of 1 kilogram of steel is 

 effected within, say, another quarter of an hour, successive fusions 

 being made in somewhat diminishing intervals of time. It is 

 quite feasible to carry on this process upon a still larger scale by 



