PRODUCTIONS OF THE HIMALAYA. 



249 



drive off the volatile ingredients, sulphur, and arsenic ; and to oxidate the 

 iron, thereby promoting the fusibility of the ore, and consequent separa- 

 tion of the copper from the scoria when in fusion : and, secondly, by an 

 intense and properly directed fusing heat, to effect the vitrification of the 

 impurities ; which thus form a slag at the top, and are skimmed off, while 

 the metal sinks down in a comparatively pure state. To promote this 

 vitrification of the ingredients, occasional additions are made to the ore, as 

 the case may seem to require ; though, in general, the run of the ores is 

 such, as to require little beyond a few slags of an old smelting. Calcareous 

 flux has been used at some works ; and this is at hand in the mountains. 

 A most valuable and effective flux, for the reduction of ores, in the small 

 way, (for experiment) is borax. Whether it might not be used on the large 

 scale, here, where it is so much cheaper than in Europe ; may require 

 some consideration, and some practical trials. 



The operations of roasting and smelting are repeated several times — 

 each smelting being followed by a roasting — ^to expedite which effect ; the 

 copper is after each smelting, but the last, let into water to be granulated. 

 This separation of the metal into such small parts, assists of course, the 

 calcining power of the furnace, and the work is more speedily effected than 

 if performed on the mass. After the last smelting comes the process of re- 

 fining, or poling, as it is technically called. It consists in keeping the copper 

 in a melted state, covered with charcoal ; and introducing from time to time 

 a Avooden pole into the melted metal ; which causes considerable ebullition, 

 owing to the evolution of gaseous matter. It is occasionally assayed, in 

 order to judge how the process is going on ; by taking out a small portion, 

 allowing it to cool, and breaking it in the vice. By the colour and general 

 appearance of the fractured surface; a judgment is formed, as to whether 

 the poling has proceeded far enough. This operation which gives the 

 metal that perfect appearance, always looked for in the market ; is 



3 R ifnknown 



