524. ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



do much more with that method, toward the direct manu- 

 facture of iron, than had been done as a secondary result, be- 

 cause it is impossible to bring more carbon into play in a 

 liquid condition than is contained in the cast iron ; and that 

 the presence of carbon in a liquid state is necessary for the 

 reduction of ores in a rotary hearth. There can be no doubt, 

 however, that contact is more intimate and action conse- 

 quently more energetic between the carbon and ore in a fluid 

 condition than when solid. Indeed, the reducing action of 

 gaseous carbon, as carbonic oxide, is not as energetic, since 

 the temperature must be lower, or contact with the melted 

 ore less perfect. Still it is indisputable that under condi- 

 tions present in Dank's apparatus the reduction of ore may 

 be aided by the addition of pure, finely divided vegetable or 

 mineral carbon, since by rotation more intimate contact of 

 the carbon and the more or less molten ore would take place, 

 and consequently more energetic action. The treatment of 

 pure iron ores in this manner, in common puddling furnaces 

 in Styria and elsewhere, in the first part of the century 

 abandoned because not economical supports this assump- 

 tion. The old methods, as w^ell as the recent experiments for 

 the direct manufacture of malleable iron from unfused ore, 

 made use of a temperature lower than that of the blast fur- 

 nace, and were consequently very slow and variable. Ele- 

 vation of the temperature to the fusion of the ore produced 

 iron slag, reducible with difficulty for the want of free access 

 of the reducing gases, and the molten portions rapidly es- 

 caped from the action of the solid and gaseous carbon. The 

 behavior of a sample of slag in a carbon crucible, in a very 

 fluid condition, shows, however, that the reduction of iron 

 from slag by carbon may be very rapid wdien contact is inti- 

 mate. In more recent experiments, in the direct manufact- 

 ure, the reduction of the ore has either been a separate 

 process, according to Gerstorf and Chenot, or, by a continu- 

 ous process, the reduced ore, without cooling, has been car- 

 ried on, in an apparatus consisting of diflerent separate but 

 connected hearths, to the finished bloom, as in Yates' meth- 

 od. In all these the reduction is accomplished by mixture 

 with fine coal, and external heating, slowly, to be sure, but 

 effectually, even to the formation of some cast iron, but the 

 difficulties begin in the economical separation of the iron 



