226 THE SCIENTIFIC PAPERS OF 



steel to this temperature ; and assuming the latent heat of fusion 

 of steel at 29'5 units (silver is 21, and zinc 28), there are roughly 

 450 units required to melt a gram of steel, and 225,000 to melt 

 half a kilogram, that is about f of the heat generated in the 

 crucible, and \ of the horse-power actually expended. A good 

 expansive condensing steam engine converts the heat energy re- 

 siding in coal into mechanical energy, with a loss of over eighty 

 per cent., or, in other words, \ only of the 7,000 units residing in 

 a gram of ordinary coal is represented as work in the engine. It 

 hence follows that the useful effect attainable in the electric fur- 

 nace is \ x i = Jy- of the heat energy residing in the fuel consumed 

 under the boiler of the engine. 



To melt a gram of steel in the electric furnace takes, therefore, 

 450 x 18 = 8,100 units, which is within a fraction the heat actually 

 contained in a gram of pure carbon. It results from this calcula- 

 tion that, through the use of the dynamo-electric machine, worked 

 by a steam engine, when considered theoretically, one pound of 

 coal is capable of melting nearly one pound of mild steel. To 

 melt a ton of steel in crucibles in the ordinary air furnace used at 

 Sheffield, from 2| to 3 tons of best Durham coke are consumed, 

 the same effect is produced with one ton of coal when the crucibles- 

 are heated in the regenerative gas furnace, whilst to produce mild 

 steel in large masses on the open hearth of this furnace, 12 cwt. of 

 coal suffice to produce one ton of steel. The electric furnace may 

 be therefore considered as being more economical than the ordinary 

 air furnace, and would, barring some incidental losses not included 

 in the calculation, be as regards economy of fuel nearly equal to 

 the regenerative gas furnace. 



It has, however, the following advantages in its favour: 1st, 

 That the degree of temperature attainable is theoretically un- 

 limited. 2nd. That fusion is effected in a perfectly neutral atmo- 

 sphere. 3rd. That the operation can be carried on in a laboratory 

 without much preparation, and under the eye of the operator. 

 4th. That the limit of heat practically attainable with the use of 

 ordinary refractory materials is very high, because in the electric 

 furnace the fusing material is at a higher temperature than the 

 crucible, whereas in ordinary fusion the temperature of the crucible 

 exceeds that of the material fused within it. 



"Without wishing to pretend that the electric furnace here repre- 



