a8 to fuse the galena and thus check the smelting. _ 
Hot Blast in the Smelting of Lead. 171 
thick, leaves the inside space about four and a half inches by 
twelve and a half. The blast passes into this chest by a pipe at 
E and out at F, whence by a curved pipe it is discharged into the 
fire through a ‘twyer’ cast in the air-chest at G, two inches above 
on level of the lead reservoir. 
Fig. 2. 
The lead reservoir A (fig. 2,) is filled with metallic tent; cwhieki 
in the process of smelting continues in a state of fusion, and while 
the furnace is used is not withdrawn. The ‘charge’ in the pro- 
cess of smelting, floats upon the melted lead, and the metal as 
smelted falls into it, flows over and discharges through the groove 
in the hearth. In working the furnace, the smelter throws im- 
mediately in front of the blast, two or three billets of light wood, 
say two inches in diameter and sixteen inches long, upon which 
are thrown up the ‘charge’ in process, and fresh galena, filling 
the furnace near even with the top of the air-chest and sloping 
down to the hearth. The blast being let on, strikes upon the 
billets of wood and is thus diffused evenly through the vast 
charge, carrying with it the flame of the fuel. 
It will be perceived that the air passing into the hollow chest, 
acts as a refrigerator upon the inner walls, and thereby prevents 
their being heated so high as to combine with the sulphur, by 
which they would soon be destroyed ; and also by preventing an 
accumulation of héat in the walls, keeps the furnace of a uniform 
ure, which if not thus moderated would soon run so-hi 
