56 



LEAD 



assay of the ores smelted during the year was 75 J, the yield from the smelting fur- 

 naces was 68 per cent., and the coal used per ton of ore was 13| cwts. The lead 

 recovered from the slag and fumes amounted to 2| per cent., making the total yield 

 of metal 71 i per cent., and the loss on the assay produce 4| per cent. 



In this establishment the men are paid from 7s. Gd. to 12s. 6d. per ton of lead, in 

 accordance with the nature of the ores operated on. 



In one establishment the process before described is somewhat varied. The charge 

 employed is 21 cwts. This is run down and tapped off at the expiration of 6 hours, 

 and about 9 pigs of 1 cwt. each usually obtained. A second charge of 21 cwts. is 

 then dropped in, and. as soon as it is roasted, mixed with the slags of the former 

 operation. The whole is then run down in the ordinary way, the slags drawn and the 

 lead tapped off in 9 hours. The produce of the second or double charge is from 14 

 to 15 pigs. 



If the ores are difficult to flow, 16 to 16 hours are required for the two charges. 

 A small quantity of black slag from the slag hearth is employed for drying up. 



Figs. 1331, 1332, 1333, represent the reverberatory furnace at the Marquis of 

 Westminster's lead-smelting works, two miles from Holywell. The hearth is hollowed 

 out below the middle door of the furnace ; it slopes from the back and ends towards 

 this basin. The distance from the lowest point of this concavity up to the sill of the 

 door, is usually 24 inches, but it is sometimes a little less, according to the quality of the 



1331 



1332 



1333 



ores to be smelted. This surface has no hole for running off the slag, above the level 

 of the tap-hole for the lead, like the smelting furnace of Lea, near Matlock. A single 

 chimney stack serves for all the establishment ; and receives all the flues of the various 

 roasting and reducing furnaces. Fig. 1333 gives an idea of the distribution of these 

 flues, a a a, &c., are the furnaces ; b, the flues, 18 inches square ; these lead from 

 each furnace to the principal conduit c, which is 5 feet deep by 2 wide ; d is 6 feet 

 deep by 3 wide ; e is a round chamber, 15 feet in diameter ; /is a conduit, 7 feet high 

 by 5 wide ; g another, 6 feet high by 3 wide. The chimney at h has a diameter at 

 bottom of 30 feet, at top of 12 feet, including the thickness of its sides, forminga trun- 

 cated cone 100 feet high ; whose base stands upon a hill a little way from the furnaces, 

 and 62 feet above their level. 



a, figs, 1331, 1332, is the grate ; 5, the door of the fire-place ; c, the fire-bridge ; 

 d, the arched roof; e, the hearth; // /, &c., the working doors; g g, flues running 

 into one conduit, which leads to the subterranean condensing-chamber e, and thence to 

 the general chimney ; h, a hopper-shaped opening in the top of the furnace, for sup- 

 plying it with ores. 



This magnificent structure is not destined solely for the reduction of the ores, but 

 also for dissipating all the vapours which might prove noxious to the health of the 

 work-people and to vegetation 



