SfX WILLIAM SIEMENS, F.R.S. 22$ 



and injury to the brickwork, from the in-draught of cold air 

 through crevices, which is otherwise unavoidable in any furnace 

 worked without blast. 



The action of the furnace is regulated by the chimney damper, 

 and by valves governing the supply of gas and air, and the draught 

 is reversed by cast-iron reversing valves, on the principle of the 

 common four-way cock. 



FUSION OF STEEL IN CRUCIBLES. In the application of the 

 system to the fusion of steel in closed pots or crucibles, the 

 melting-chamber, containing generally 24 pots, is constructed in 

 the form of a long trench, 8 feet 6 inches wide at the bottom, and 

 gathered in to under 2 feet at the top. The sides of the melting- 

 chamber are arched both horizontally and vertically, to keep them 

 from sinking together in working, and the work is strengthened 

 by cross walls at intervals. The pots are set in a double row along 

 the centre of the melting-chamber, and the flame passes from 

 side to side, the gas and air from the regenerators being intro- 

 duced alternately from one side and from the other, opposite to 

 each pair of pots. The melting-chamber is closed above by loose 

 firebrick covers, which are drawn partly off in succession by 

 means of a lever suspended from a pulley above the furnace, when 

 the pots are to be charged or drawn out. The pots stand in a bed 

 of finely-ground coke-dust, resting on iron plates. The coke-dust 

 burns away only very slowly, if it is made of hard coke and finely 

 ground, and it presents the great advantage of remaining always 

 in the form of a loose dry powder, in which the pots stand firmly, 

 while every other material that I have tried either softens at the 

 intense heat, or sets after a time into a hard, uneven mass, in 

 which the pots do not stand well. 



The process of melting carried out in this form of gas furnace 

 is the same in all respects as that in the small air furnaces or 

 melting-holes fired with coke which are commonly employed, but a 

 great saving is effected in the cost of fuel, and in the number of 

 crucibles required. 



The ordinary consumption of hard coke, costing 22s. per ton in 

 Sheffield, is between three and four tons per ton of steel fused, 

 while in the gas furnace the same work may be done by the 

 expenditure of 15 to 20 cwt. of common coal slack (worth only 

 5s. to Ss. per ton), at a cost that is of only 5s. against 75s. per ton 



