TIN 



1005 



In the first a mixture of the ore with anthracite was exposed to heat on the hearth 

 of a reverberatory furnace fired with coal. 



In the second, the tin ore was fused in a blast-furnace, called a blowing-house, sup- 

 plied with wood-charcoal. This method is not now practised in England. 



In the smelting -Jiouses, where the tin is worked in reverberatories, two kinds of fur- 

 naces are employed ; the reduction and the refining furnaces. 



Figs. 1989 and 1990 represent the furnaces for smelting tin at Truro, in Cornwall : the 

 former being a longitudinal section, the latter a ground plan, a is the fire-door, through 

 which pitcoal is laid upon the grate b ; c is the fire-bridge ; d, the door for introducing 

 the ore ; e, the door through which the ore is worked upon the hearth/; y, the stoke- 

 hole ; h, an aperture in the vault or 

 roof, which is opened at the discharge 

 of the waste schlich, to secure the 

 free escape of the fumes up the 

 chimney ; i, i, air-channels, for ad- 

 mitting cold air under the fire-bridge 

 and the sole of the hearth, with the 

 view of protecting them from injury 

 by the intensity of the heat above. 

 k, k, are basins into which the melted 

 tin is drawn off; I, the flue ; in, the 

 chimney, from 35 to 50 feet high. 

 The roasted and washed schlich is 

 mixed with small coal or culm, along 

 with a little slaked lime, or fluor- 

 spar, as a flux ; each charge of ore 

 amounts to from 15 to 24 cwts., and 

 contains from 60 to 70 per cent, of 

 metal. 



Fiff. 1991 represents in a vertical 

 section through the tuyere, and Jiff. 

 1992, in a horizontal section, in the 

 dotted line x, x, of Jiff. 1991, the fur- 

 nace employed for smelting tin at the 

 Erzegebirge mines in Saxony, a, are 

 the furnace-pillars, of gneiss ; b, b, are 

 shrouding or casing walls ; c, the 

 tuyere wall; d, front wall, both of granite ; as also the tuyere e. f, the sole 

 stone, of granite, hewn out basin-shaped ; g, the eye, through which the tin and slag 

 are drawn off into the fore-hearth h ; i, the stoke-hearth ; 

 k, k, the light ash-chambers ; I, the arch of the tuyere ; 

 m, m, the common flue, which is placed under the furnace 

 and the hearths, and has its outlet under the vault of the 

 tuyere. 



In the smelting-furnaces at Geyer the following dimen- 

 sions are preferred : length of the tuyere -wall, 1 1 inches ; 

 of the breast wall, 11 inches ; depth of the furnace!7 inches. 

 High chimney-stalks are advantageous where a great 

 quantity of ores is to be reduced, but not otherwise. 



The refining furnaces are similar to those which serve 

 for reducing the ore ; only, 

 instead of a basin of recep- 

 tion, they have a refining 

 basin placed alongside into 

 which the tin is run. This 

 basin is about 4 feet in dia- 

 meter, and 32 inches deep ; it 

 consists of an iron pan, placed 

 over a grate, in which a -fire 

 may be kindled. Above this 

 pan there is a turning gib, by 

 means of which a billet of 

 wood may be thrust down 

 into the bath of metal, and kept there by wheeling the gibbet over it, lowering a rod, 

 and fixing it in that position. 



Formerly in Cornwall nearly all the tin was smelted in blast-furnaces; these works 

 were called blowing-houses. The smolting-furnaces were 6 feet high from the bottom 



1991 



1992 



