462 



Mr. J. Napier o?i Copper Smelting. 



Table II. — Cuba ore not analysed before being put into the 

 furnace. 



These results speak for themselves. By casting the eye along 

 the sulphur line, it will be observed that there is generally an 

 iniirease of sulphur in the top beds, showing evidently that the 

 air passing over them had been charged with sulphur ; and where 

 it is not cooled so as to deposit its sulphur, no change is effected 

 excepting the heating of the ore. 



To have a fair comparison, a single bed and a three-bedded 

 calciner were charged with the same quality of ore, and each 

 charge kept in the same length of time, the heat, stirring and 

 other circumstances being kept, as near as possibly could be, the 

 same. The quantity of sulphur only was estimated. The ore 

 put in contained 26'5 per cent, sulphur. 



These numbers speak in favour of a single bed calciner. One 

 great drawback to the compound furnace is the regulating of the 

 fire ; this must be done to suit the ore upon the lowest bed, which 

 is often not suitable to the charges in the upper beds, and conse- 

 quently absorption of sulphur takes place. Trials have been 

 made with three-bedded calciners, open at each end, the fireplace 

 being enlarged ; the fii-e plays over each bed, and the sulphur 

 fumes are all carried away on the opposite end by the stack or 

 culvert without passing over another bed, but with no other result 

 than an increased consumption of fuel without any corre- 

 sponding advantage. 



We shall have an opportunity of entering more fully into the 

 principles and reactions of the calcining process when treating 

 of the calcination of the mat or coarse metal, which, being free 

 from earthy matters, and more definite in composition, the action 



