LEAD 



furnace works off about seven tons of roasted ore in the course of 24 hours ; the 

 weight of slags run off is about double that of the lead obtained, and the matt re- 

 moved from the surface of the pan is nearly 5 per cent, of the lead produced. The 

 ores treated in this establishment consist of galena, much mixed with spathose iron, 

 and are therefore somewhat refractory. A. furnace of this kind requires for its con- 

 struction about 1,000 segmental fire-bricks, and the same number of ordinary fire- 

 bricks of second quality. 



Figs. 1338, 1339, 1340, and 1341 represent respectively a vertical section, an elevation, 

 a ground plan, and an horizontal section of a Castilian furnace. The section .%. 1341 



1340 



1341 



is on the line XY,/^. 1339. A is the body of the furnace, B, the bottom, composed of 

 a mixture of coke-dust and fire-clay ; c c c, the tuyeres ; D, the rectangular covering of 

 masonry ; E E E E, cast-iron pillars ; F, the breast-pan ; G, slot for tapping hole ; H, lip 

 of breast-pan ; i, feeding-door ; K, flue-hole ; P, o, ground line. 



1342 







Figs. 1342, 1343 are the slag- waggons, A being a moveable case without a bottom, 

 and B a strong cast-iron plate running on four wheels. 



The desulphuration of the ores to be treated in these furnaces may be effected either 

 by the aid of an ordinary reverberatory roasting furnace, or in heaps, or properly 

 constructed kilns. 



The kilns best adapted for this purpose consist of rectangular chambers, having an 

 arched roof, and provided with proper flues for the escape of the evolved gases, as 

 well as a wide door for charging and withdrawing the ore to be operated on. 



Each of these chambers is capable of containing from 25 to 30 tons of ore'; and, 

 in order to charge it, a layer of faggots and split wood is laid on the floor, and this, 

 after having been covered by a layer of ore about two feet in thickness, is ignited, 

 care being at the same time taken to close, by means of loose brick -work, the open- 

 ing of the door to the same height. When this first layer has become sufficiently 

 ignited, a fresh stratum of ore, mixed with a little coal or charcoal, is thrown upon it, 



