54 EIGHTH REPORT — 1838. 



purpose of more easily conveying the ladles filled with crystals from 

 pot to pot. 



AH this being provided, one of the large pots is filled with lead, con- 

 taining silver, say 10 oz. per ton, and after it is melted and skimmed, 

 the fire is withdrawn, the damper put down, and the ash-pit door 

 closed, when it cools and crystallizes as already described. Crystals, 

 as they are formed, are laded out into the second pot until about three- 

 quarters of the whole have been removed, which will contain about 5 

 ounces of silver per ton : upon this the operation is repeated, giving lead 

 2 ounces ; and by a third crystallization, there is obtained from this, 

 poor lead, holding not more than 10 to 15 dwts. of silver per ton, 

 which is cast into pieces for sale as separated lead. The rich lead, on 

 the other hand, is collected and repeatedly crystallized, until it is made 

 to contain 200 or 300 ounces per ton, after which the silver is extracted 

 by cupellation. In working, the different pots at each stage are filled 

 up always with lead of the same content of silver before beginning to 

 crystallize, and a greater or less amount of crystals taken out, as the 

 operator may think fit, in which respect the practice differs almost at 

 every establishment ; but the process is so very simple and the mode 

 of proceeding so obvious, that it is unnecessary to give a more minute 

 detail. 



By operating in the way described, it is evident that but a very small 

 portion of lead is made to undergo the process of cupellation, not more 

 than one twentieth part, when 10 ounces of lead is enriched to 200 

 ounces by repeated crystallization ; and as the loss by separation has 

 not been found to exceed a 250th part of the whole lead, the loss by 

 the joint processes becomes -^^^ of g^j + zio' '^^' a^iout one part in 

 120. The expense of separation is something less than that of cupel- 

 lation, so that by the reduction of expense and the reduction of loss of 

 lead, the extraction of silver is so far economized that 3 ounces per 

 ton will now fully cover the whole charge. 



By this reduction of the cost of extracting the silver, all the lead of 

 Alston Moor (22,000 tons), Devon, Cornwall, and West Cumberland 

 (2000), and the lead of North Wales (12,000), making a total of 

 36,000 tons per annum, can now be made to yield up its silver with ad- 

 vantage, so that on the very low average of 6 ounces per ton, at least 

 54,000 ounces of silver per annum are gained by the arts. There may 

 also be safely estimated a reduction of the loss of lead on the 18,000 

 tons generally I'efined by cupellation of at least 300 tons. The lead 

 obtained by separation is much improved in quality, being more soft 

 and ductile than ordinary lead. 



It only remains to consider, how it happens that lead in the act of 

 consolidation gives up a portion of its silver to the suiTounding and 

 still fluid lead ; and the most simple view of the matter is, undoubtedly, 

 that it is an instance of true crystallization, in which the homogeneous 

 particles of lead arc dra\vn together by virtue of their molecular at- 

 traction, to the exclusion of the foreign body, silver. On examining 

 the crystals, it is true, no trace of regular form can be perceived ; but 

 this could scarcely be expected, from their being so much agitated and 



