The Madisonian. [volume] (Washington City [i.e. Washington, D.C.]) 1837-1845, 1841-04-20

ed that the heat could not be made of sufficient
intensity by this process 10 obtain all the lead the
mineral contained, consequently scupola furna-
ces were constructed in the following manner :
large oven was first built, to which was con-
nected stack or chimney of from forty 10 fiji
ty nheight, for the purpose ofgivins strong
draught to the fire, and thereby increasing the
heat the mineral was then placed in this oven
intermingled with charcoal, lagos and quick
lime, when the combustibles were ignited, and
the oven, with the exception OF small vent-holes,
is closed up, and the lead as il is separated from
the sulphur, sinks TO the bottom Of the oven, and
IS drained of into basin, from which il is dip
ped by ladies into moulds. But these furnaces,
from the cost Of construction, and from the con-
slant need OF repair, have given way TO blast
furnaces which are now generally used. These
are constructed similar TO blacksmith's forge,
havinga large bellows which is worked by water
power, and the mineral, after being beaten up
into small PARTICLES, is placed on the forge in
small quantities mixed with charcoal, lime, and
small pieces Of pine or linn wood, where, by the
means Of the bellows, strong heat is produced.
The lead, when separated, Iuns off on an ncli-
ned 'apron into an iron vessel, from which it IS
dipped into moulds. These furnaces, when well
managed, cause the ore 10 produce more lead
than any others yet introduced, but an inexperi-
ehced smeter may produce contrary effects with
them in several ways: for fnsrance, il 100 much
ore be put ON at one time, or il the heat is not
kept uniform, portion of the lead will combine
with the charcoal and lime, and form 'slug;' or
should the heat be too great the lead is rendered
brittle and Of an inferior quality.
The chemical change produced in the smelling
of lead is, that the sulphur is driven offby means
of the heat. The charcoal at the same time abb
serbs the oxygen which has, by exposure 10 the
air, combined with the ore the lime also absorbs
the sulphuric acid, which is formed by the union
of the sulphur Of the mineral, the oxygen of the
air and the water from the wood, which forms a
sulphate of lime. The meta. being thus freed
from other substances by theh heat, becomes fused,
and from its specific gravity, sinks TO the bottom
and runs of.
MINERAL.
From observations by the miners, il has bee n
discovered that there are several external OBJ
jects which denote the existence of lead ore. Ii
has been remarked that blue grass alone grows
in the vicinity of mineral. Ii has also been per-
ceived that over a heavy body of mineral there
is a sway or concavity in the external appearance
of the earth likewise over perpendicular crew.
ces peculiar vegetation has been found TO exist
An interesting and somewhat singular occur
renee in mining is, that perpendicular crevces
running north and south, seldom, if ever, con-
tain lead ore, while those running east and west
are seldom found without more or less in them.
These last two are sometimes found to run for
miles in a straight line, crossing several raynes
in their course; thus when perpendicular Gre
vice, running east and west, is found to contain
mineral, on one bluff its course is taken, and
shafts are sunk on the adjoining bluff.