5/7? WILU 'AM SIEMENS, F.R.S. 329 



self introduced the system of reduction by a rotator in 1868, and 

 illicit state the results he obtained. The cheapest and most 

 direct method of reducing iron ore was in a rotary furnace ; the 

 iron ore and the carbonaceous material were introduced at one 

 end of a large rotating cylinder, and brought out in the condition 

 of spongy iron continuously at the other end ; nothing could be 

 simpler or cheaper, but still he saw reason to abandon it. First, 

 because the spongy iron thus obtained absorbed in the very process 

 a good deal of sulphur, and this could not be remedied unless you 

 could prevent its contact with the sulphurous acid produced in the 

 combustion of the coal. Then, again, it was not easily dissolved 

 in the bath of metal, even if that were sufficient, because it floated 

 on the top, and rapidly oxidised under the influence of the flame 

 of the furnace. Moreover, unless you used such materials as could 

 not practically be employed on a large scale, the spongy iron 

 became enclosed in the gangue of the ore, and would not melt in 

 the metallic bath, the gangue forming a screen which prevented 

 intimate contact between the fluid and the solid sponge. He 

 therefore modified the process without abandoning the principle of 

 the rotary furnace, and now raised the heat to the point of 

 melting, not the ore but the gangue contained in it, and thus 

 effected the reduction. The result was a metallic ball enveloped 

 in scoria, which did not absorb sulphur, and which could be 

 hammered out into bars, or transferred to the open hearth furnace 

 and melted down into steel. He believed that would be found the 

 cheapest and most direct method. He alluded chiefly to the pro- 

 duction of mild steel in large quantities ; with regard to tool steel 

 he was not sure if the presence of a little foreign matter, such as 

 silicon and sulphur, should be entirely avoided. The famous hard 

 steel of India contained a considerable proportion of these 

 elements, and generally compounds ol' iron were harder than the 

 pure metal. 



