On Smelting cf Lead. 187 



provement ; wlthoul, however, presuming to say, how far 

 it may be expedient to adopt the proposed aherations; be- 

 ing sensible that what mav appear verv feasible in theory, 

 or may even answer in small assays, may riot be practicable 

 in large works. 



" The first aUeration which I wonld propose to the con- 

 sideration of the lead-smehers, is to substiliile an horizon- 

 tal chimnev oF two or three hundred yards in length, in 

 the place of the perpendicular one now in use. In the pre- 

 ceding Essav, which was first published in 1778, metitioa 

 is made of the probability of saving a large quantity of sub- 

 limed lead, by making the smoke which rises from the ore 

 pass through an horizontal chinmey, with various windincs 

 to condense the vapour. I have since conversed with some 

 of the principal lead-smelters in Derbyshire, and find that 

 I had overrated the quantity of this sublimed lead ; the 

 weight of the scoria, from a ton of ore, amountina; to more 

 than I had supposed. They were all of them, however, of 

 opinion, that the plan I had proposed for saving the sub- 

 limate was a very rational one. But so difficult is it to 

 wean artists from their ancient ways of operating, that I 

 question verv much whether any of them would ever have 

 adopted the plan they approved, if an horizontal chimnev, 

 which was built a little time ago in Middleton Dale, for a 

 quite different purpose, had not given them a full proof of 

 the practicability of saving the sublimate of lead, which is 

 lost in the ordinary method of smelting. This chimney 

 was built on the side of a hill, to prevent some adjoining 

 pastures from beina; injuritd by the smoke of the furnace, 

 it not only answers that end, but it is found also to collect 

 considerable quantiliei of lead, which is sublimed during 

 the smeiiing of the ore. This sublimed lead is of a whitish 

 cast, and is sold to the painters at ten or twelve pounds a 

 ion ; it might perhaps be converted into red lead with still 

 Jiiore profit. 



''A second circumstance to be attended to in the smeU- 

 jng of lead ore, is the saving the sulphur contained in it. 

 1 he pure lead ore of Derbyshire contains about an eighth 

 and a ninth part of its weight of sulphur ; but as the ore 

 which is smelied is never pure, being nnxcd with particles 

 of stjor, can'k. Limestone, hfusiL and other substances, 

 which the nnners call deads, wc siiall be hi<fh cnouuh in 

 our supposition, if wc say that the ordinary ore contains a 

 tcnili of its weight of sulphur; it mav not, probablv, con- 

 tain so much, but even a twelfth part, could it be collected 

 HI a .-mall expense, would be an object of great importance 



tq 



