Mr. H. L. Pattinson on Smelting Lead Ore, 8$c. 155 



at other mills, the quantity roasted in eight hours by one man is three 

 bings, at three charges, and thus three men working each 6 eight- 

 hours' shifts, roast but fifty-four bings of ore per week. 



The manner of conducting the process of roasting is the same in all 

 cases. The proper charge of ore is spread evenly over the bed of the 

 furnace to the depth of two or three inches, and the fire is at first push- 

 ed moderately, during which the ore is frequently turned and stirred, 

 in order that the whole may be uniformly heated, but care is to be taken 

 that no part is prematurely fused. If the fire is judiciously managed, 

 the charge gradually attains a dull red heat — a greater heat is then 

 given and the ore vigorously stirred, when, in a little time, it begins 

 to feel soft and adhere slightly to the tool, in which state it is with- 

 drawn from the furnace. The roasting process is conducted in the 

 best manner, when great care is taken to apply the heat very gently at 

 first, to keep, by constant stirring and change of place, the temperature 

 of the whole charge as uniform as possible, and to withdraw it at the 

 proper time from the furnace. 



After the furnace is properly heated and working, two Winchester 

 bushels, or about 1£ cwt. avoirdupois, of free coal, are required to roast 

 one bing of ore ; but some varieties of ore can be more easily reduced 

 into the pasty state, mentioned above, than others ; that is, they fuse at 

 a lower degree of heat, and this in proportion to their purity. The 

 least fusible ores are generally the most difficult to smelt, and undergo 

 the greatest loss in that operation. It is well known that a considerably 

 greater produce of Lead can be obtained from the same ore after being 

 properly roasted, than before. This difference is of course variable, but 

 in some instances, £!0 bings of roasted ore have yielded 8 or 9 cwt. more 

 Lead than 20 bings of the same ore smelted in its raw state. 



At nearly all smelting mills long horizontal chimneys or flues are con- 

 structed (generally on the slope of an adjacent hill if practicable), which 

 the smoke from the various processes of smelting is made to traverse 

 before it escapes into the atmosphere. As the heat of the furnace in 

 roasting, if incautiously applied, may volatilize a portion of the ore, and 

 the draught has a tendency to draw along with it some of the smaller 



