Lead \ 
187 
then opened, and the lead runs into moulds placed to re- 
ceive it, where it congeals into oblong masses called pigs , 
weighing about 60 pounds each. As soon as the lead 
has run out of the furnace, the tap-hole is closed, the 
scoriae are replaced in the bed, and being quickly raised 
to a glowing red heat are soon melted ; the greatest part 
of the lead that they contained by this means collects into 
a mass at the bottom ; a little lime is thrown in as before, 
the scoriag thus rendered solid are raked aside, and the 
lead which they covered is let off into a mould. This 
second scoriae, though still holding from 5 to 8 per cent 
of lead, is now removed from the furnace, and applied to 
no purpose but that of mending roads, the expence of se- 
parating the last portions of metal being more than the 
value of the produce. 
The lead of the first running is. the best that procured 
from the scoriae being sensibly harder,, and less, malleable 
on account of the iron that it contains. 
It is a matter of doubt among the most intelligent 
smelters whether there is any advantage in retaining the 
carbonat of lead, with which the galena is very often mix- 
ed in considerable proportion. On the one hand it is cer- 
tain that it contains a large quantity of metal, and in as- 
says is very easily reducible ; but on the other hand, 
when treated in the reverberatory, it vitrifies almost at the 
first impression of the heat, and being a very active flux 
it is apt to bring the whole into fusion while much sul- 
phur still remains unsublimed ; hence the amount of 
scoriag is prodigiously increased, and with it the trouble 
of the smelters,, while the produce of lead is very little 
augmented, [2 Atkin, 14, 
The following practical remarks of the Bishop of Lam 
daff, are well worth attention. 
It is not fifty years since the blast or hearth furnace^ 
was the only one in use for smelting lead ore in Derby- 
