SIX WILLIAM SIEMENS, F.R.S. 285 



material in general use, would be rapidly melted, but a brick, 

 specially prepared by crushing pure quartz rock, and mixing it 

 with not more than '2 per cent, of quicklime to give cohesion, 

 answers well. The hearth of the furnace is made of white sand 

 with u small admixture of more fusible fine sand, which mixture 

 sets exceedingly hard at a steel-melting heat, and possesses the 

 advantage of combining into a solid mass with fresh materials 

 introduced between the charges to make up for wear and tear. 

 The hearth and the furnace-roof, if of the materials just specified, 

 are very little attacked when the Siemens-Martin process is used, 

 although the heat must be sufficient to maintain wrought iron 

 containing only a trace of carbon, in a perfectly fluid condition. 

 If pig metal and ore (previously fused with the necessary amount 

 of flux) are used, the furnace also stands well, but the use of raw 

 ore entails the disadvantage of a more rapid destruction of the 

 furnace ; even magnetic oxide of the purest description necessitates 

 the addition of raw lime for the formation of a fusible slag, and 

 the dust arising from the lime and through the decrepitation of 

 the ore causes the silica bricks to melt away rapidly, so that after 

 perhaps two months' usage, the 9-inch arch of the furnace is re- 

 duced to the thickness of from 1 to 2 inches. It is evident that 

 silica is chemically speaking an objectionable material to be used 

 in the construction of these furnaces, because it prevents the for- 

 mation of basic slags, and that a furnace bed constructed of pure 

 alumina or lime would be preferable. My friend M. Le Chatelier, 

 Inspecteur-General des Mines, whose valuable labours for the ad- 

 vancement of iron metallurgy are well known, suggested to me 

 years ago the use of Bauxite (from Baux in France, where it was 

 first discovered), a mineral consisting chiefly of alumina, for 

 making the furnace-bed, but I was not able to succeed with this 

 owing to the great contraction of the mass when intensely heated, 

 and non-cohesion with the same material introduced for the pur- 

 pose of repair. In attempting to construct the sides and roof of 

 the furnace of Bauxite bricks, these were not found to be equal in 

 heat-resisting power to silica bricks, which latter are indeed unob- 

 jectionable, except when raw ore and limestone are used. 



If good pig metal, such as is used in the Bessemer process, is 

 employed, a metal of high quality is the result, equalling in most 

 respects the steel produced by melting Swedish bars in pots by the 

 old Sheffield process. 



