166 Mr. H. L. Pattinson'ou the Smelting of Lead Ore, Qc. 



The long horizontal chimnies, or flues, mentioned at page 153, into 

 which the smoke and metallic vapours, from the roasting furnace, ore 

 hearth, and slag hearth, are conveyed, contain, at the end of some time, 

 a copious deposit called smelter's fume. This fume consists of Sulphu- 

 ret, and, probably, also of Sulphate of Lead, which have been volatilized 

 in the different processes, mixed, like hearth-ends, with a quantity of 

 earthy matter, from the lime and coal used in smelting. It is generally 

 suffered to accumulate, either in or out of the chimnies, until the end 

 of the year, when it is washed, to remove the earthy matter, and the 

 heavy residue is roasted until it coheres into lumps, and smelted in the 

 slag hearth exactly in the same way as grey slags, described at page 163. 

 The quantity of slag lead produced from the smelter's fume, deposited 

 in smelting 9751 bings of ore, was 500cwt. ; being at the rate of 5cwt. 

 Oqrs. 14lbs. of lead per 100 bings of ore. 



The proportions stated above are by no means to be considered in- 

 variable, for the quantity of lead produced at a smelting establishment, 

 from time to time, by the hearth-ends and smelter's fume, from a given 

 quantity of ore, cannot probably be very uniform, and must depend a 

 good deal upon the care and skill exercised in conducting the various 

 operations. If no more than the due degree of heat is used in each 

 process, the deposits under consideration are likely to be less than if a 

 strong heat is injudiciously applied. 



CORRESPONDENCE OF PRODUCE WITH ASSAY. 



As the smelting process is liable to great mismanagement, through 



inexperience or inattention on the part of the agents or workmen, it is 



a matter of some consequence to know how far the quantity of lead 



obtained by smelting in the large way corresponds with the absolute 



quantity contained in the ore operated upon, and, for this purpose, it is 



a common practice to have the ore accurately sampled and assayed prior 



to smelting. The purest Galena is a compound of 



1 atom Lead, 13 86-66 



1 atom Sulphur, 2 13-33 



15 99-99 



