210 
Lead . 
The spaces between the back of the chimney, the side 
and the cheek stone, are filled with old castings, bricks, or 
pieces of stone, and the joints filled up with dust or ashes ; 
the space left between the bottom of the hearth and the 
lower front bearer is called the breast ; — (f) is the sump 
or pot to contain the lead, as it flows from the hearth ; 
the space between the breast and the sump is paved with 
old castings imbedded in dust, and the joints filled with 
thin mortar grout ; near the sump is a mould for casting 
the lead into pigs. 
The hearth is prepared for working, by slightly ram- 
ming into the bottom a quantity of coal ashes ; the sump 
is also filled, and the space between it and the breast ; the 
dotted part f gg gj fig. 3, represents the coal ashes : the fire 
is next lighted, and when the interior of the hearth has ac- 
quired a good red heat, the smelter throws on a few sho- 
vels full of gray slags (which have been previously broken 
to the size of an egg), and as the hearth settles, occasion- 
ally adds fuel or more slags as may be required : in a few 
minutes after charging with the slags a small perforation 
is made in the breast by passing a pointed iron rod 
through the ashes close to the bearer ; the liquid scoriae 
and lead flow through this opening down the inclined 
plane formed by the ashes ; as they become hot the lead 
filters through them, and finds its way into the sump ; 
the scoriae from its viscidity remaining on the surface, 
from whence it is removed occasionally as it cools and be- 
comes hard. 
The slag hearth is continued working for 12 or 14 
hours, the smelter adding materials occasionally as requir- 
ed, and judging of the proportion of fuel by the heat and 
appearance of the fluid scoria. 
At the conclusion of the day’s work the hearth is suffer- 
ed to burn down as low as possible ; and when the scoria 
ceases to flow, the bellows are stopped, the scoria on the 
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