WILLIAM SIEMENS, F.R.S. 



393 



constructing ships of very mild steel, and the British Admiralty 

 n'\v use it largely in naval construction, with such results as I 

 k'lu-vc will shortly be placed before another Institution by their 

 chit f constructor, Mr. Barnaby. 



Although I have described the open-hearth process, as dealing 

 with pig metal and ore or, when it can be had, pig and scrap metal 

 my attention has been directed for many years to the accomplishment 

 of a process, in which the ore used is put through a preparatory pro- 

 cess of reduction and precipitation, and only a minimum quantity 

 of pig metal is employed to impart fluidity to the mass in the melting- 

 furnace. In my early experiments in this direction I followed the 

 lead of Chenot and others in producing what is called spongy iron, 

 or iron deprived of its oxygen by heating it to redness, in com- 

 Mi.ation with carbonaceous material. I soon convinced myself, 

 however, that no practical results could be obtained by this means, 

 inasmuch as the spongy iron contains, bound up with it, the gangue 

 of the ore, which can with difficulty be separated from the metal, 

 and afterwards encumbers the melting-furnace with excessive slag. 

 All the hurtful impurities contained in the ore, such as sulphur, 

 phosphorus, arsenic, &c., remain, moreover, in the spongy iron ; 

 and, as regards sulphur, its quantity is much increased on account 

 of a powerful absorbing action, exercised by the spongy iron upon 

 the sulphurous acid contained in the flame of the furnace. It was 

 necessary, therefore, to devise some plan by which the metallic 

 iron could be simultaneously separated both from the ore and its 

 impurities. This object I have succeeded in accomplishing by 

 means of a rotating furnace, which has, however, hitherto received 

 only a limited application. The furnace, which is represented 

 in Plate 47, consists of a gas-producer, the air-regenerator, a 

 reversing- valve, and the revolving drum. No gas regenerators 

 are employed in this furnace, but the gas passes from the pro- 

 ducers through an oblong channel continuously into the revolving 

 chamber, where it is brought into contact with the heated current 

 of air passing in from one or the other of the air regenerators. 

 The flame thus produced rushes forward into the heating chamber, 

 and after heating the material therein, passes back again towards 

 the inlet side, whence the products of combustion pass through the 

 second air regenerator and the reversing valve into the chimney 

 stack. By this arrangement the front of the rotatory furnace is 



