144 



which would have cost, for materials and wages, 24«, If we 

 assume the price of the mixed ore at £10 per ton, the cost of 

 32 cwt,, with that of smelting it, will be £17 is., and the 

 produce one ton of pig-lead. 



" We have now to consider what would be the produce of 

 this ore had it been smelted in the reverberatory ; and first, it 

 is necessary to refer to its assay. The assay masters adopt 

 different methods : sometimes they use fluxes ; sometimes they 

 dry the ore ; but the most usual practice, and that most re- 

 lied on by the smelters, who purchase on the faith of the 

 assay, is to test the ore in the same moist state in which it is 

 brought direct from the heaps, and without any flux, in order 

 that the assay process may more nearly represent the process 

 of the smelter. I therefore adopted this last method. Ten 

 ounces of the mixed ore were melted in an iron crucible, and 

 treated in the usual manner. In this process, all the sulphur 

 that the conjoint action of heat and air is inadequate to expel, 

 was abstracted by the afiinity of the iron of which the crucible 

 is made, and on this account a new crucible answers best. 

 The button of reduced lead weighed 7 oz. 11 dwts,, or very 

 nearly. This would indicate 75 per cent, of metal, but as 

 the assay produce is never realized by the reverberatory, the 

 actual return would be about 70 per cent, of lead ; and 71 per 

 cent, was the average produce at a great smelting-house in 

 Wales, from ores amounting in the aggregate to 36,000 tons. 

 At another house the average was 75 per cent. Other trials 

 returned 67.5 per cent., and sometimes only 50. According 

 to Bishop Watson, the Derbyshire smelting-houses averaged 

 but 67 per cent. It is probably about the truth to assume 

 that the ores on which I experimented would have returned 

 70 per cent, in the reverberatory. 



" At this rate, in order to produce one ton of pig-lead, it 

 would be necessary to smelt 28^ cwt. of ore, which, at £10 

 per ton, would be £14 5s. The cost of smelting in Flint- 

 shire, by the reverberatory, may be averaged at 30*. per ton 



