160 Mr. H. L. Pattinson on the Smelting of Lead Ore, $c. 



filtering down through all parts of the brouse into the hearth bottom, 

 flows through the channel o, Fig. 1. into the pot^ out of which it is 

 laded into a proper mould, and formed into pigs. 



The principal particulars to be attended to in managing an ore 

 hearth properly, during the smelting shift, are these : First. — It is very 

 important to employ a proper blast, which should be carefully regulated, 

 so as to be neither too weak, nor too powerful. Too weak a blast would 

 not excite the requisite heat to reduce the ore, and one too powerful, 

 has the effect of fusing the contents of the hearth into slags. In this 

 particular no certain rules can be given ; for the same blast is not suit- 

 able for every variety of ore. Soft free-grained Galena, of great spe- 

 cific gravity, being very fusible, and easily reduced, requires a moderate 

 blast ; while the harder and lighter varieties, many of which contain 

 more or less iron, and are often found rich in silver, require a blast con- 

 siderably stronger. In all cases, it is most essential, that the blast 

 should be no more than sufficient to reduce the ore, after every other 

 necessary precaution is taken in working the hearth. Second. — The blast 

 should be as much divided as possible, and made to pass through every 

 part of the brouse. Third. — The hearth should be vigorously stirred, at 

 due intervals, and part of its contents exposed upon the workstone ; 

 when the partially fused lumps should be well broken to pieces, and 

 those which are further vitrified, so as to form slags, carefully picked 

 out. This breaking to pieces, and exposure of the hottest part of the 

 brouse upon the workstone, has a most beneficial effect in promoting its 

 reduction into lead ; for the atmospherical air immediately acts upon 

 it, and, in that heated state, the sulphur is readily consumed, or con- 

 verted into sulphureous acid, leaving the lead in its metallic state ; 

 hence it is, that the reduced lead always flows most abundantly out of 

 the hearth, immediately after the return of the brouse, which has been 

 spread out and exposed to the atmosphere. Fourth, the quantity of 

 lime used, should be no more than is just necessary to thicken the brouse 

 sufficiently ; as it does not, in the least, contribute to reduce the ore 

 by any chemical effect : its use is merely to render the brouse less pasty, 

 if from the heat being too great, or from the nature of the ore, it has a 



