,a fwt 2 inches long, 5 feet 2 inchrs in dium?+er
at the Ia-ge end, and 3
fert at the SnAler
Pnrl. ‘ThP ore is ful in at the larger,
and worked np to
the smaller
end b,y nwnns of teeth 61/a inrhes wide and high, set slanting.
From the washer,
ihe “PP passes into a rmdving
screen attached
to it.
‘The pieces which are too large
The meshes of this ScrPe” are 35/& inch.
to pass through
this Srree” are sorted by hand, and the “Pe sent at once
to t,he work
The si,irious
OF? Llrposited
by +hP vnter
is wwashed
in the
roller before being budrlled.
Sometimes
+h? ~nrihy ow occurs hurl enough,
and Sufficiently
free from sand, to riispense with mashing.
The buddles used are of the regular
Colnish patter”,
the pulp being fed
at the wntre,
and the d&hargr
being on th? circumference.
The sand
pile, when formed in the huddle, is 13 feet 8 inches in diameter,
and 2 feet
deep on a” average, being higher in the centw,
and sloping down towards
the margin.
Each buddk
holds about tifiee”
tons.
Swepps, five feet i”
length, attached
to revolving
arms, push the puip along as it runs over the
conici~l pile alrearlg formed,
swving
to keep the surface in good condition,
snd facilitating
ihe deposition
of the particles
according
to their specific
g,rauitirs.
When n huddle is finished,
the pile is divided
into concentric
rings.. The innermost
of these is regarded
as ore, and, after a little
more
treatment,
sent to the works;
the next is reworked
in the same huddle,
Keeves are also employed.
These
nnd the third portion
in another huddle.
and 3 feet deep.
are 3 feet ,in diameter
at the top, 2 feet at the bottom,
After stirnng
the ore thoroughly
with water till the tub is full, it is allowed
to settle, the keeve meanwhile
being tapped with a” iron bar.
A continuous
jig is being tried for concentrating
the sand. The dress&
ore is transported
to the smelting
works,
which
are situated
in South
BethlehPm,
about four mil?s distant,
by wa,qons draw”
by four mules each,
and carrying
31,* tons.
Hetallur~,iea7
Prooeases.-The
oxidized
,,res used for the preparation
of
zinc-white
genernlly
contain
about, 20 per cpnt of zinr.
Three hundred
pounds of ore, mixed wit1r on? h”“dWd
ant, fifty pounris “f pen or dust cua,,
arc fed together
through
chill?&iron
rollers
and the” on to a Strep” for
the purpose of sizing. Fine and coarse ores are not treated together
though
subjected
to the same subsequent
process, which consists in a volat&atio”
of the oxide of zinc by heat, B cooling
of the gas.:s, and the collection
of
the zinc-white
in 1on.g bags of ordinary
muslin,
the gaseous substances
passing through
the interstices
in the cloth.
The furnaces
are of two kinds, single nnd donble. The former are charged
only at Oqe end, and only hold B little
over a third of the charge of the
latter,
which are provided
with a working
door at either end. The single
furnaces
are 5 feet long and 3 feet WidP, covered wit,, an arch of firebrick
which, at the centre, is three feet above the hearth.
The opening intO the(
flue is 18 inch-s sqnare, and the hearth consists of a” iron grate made of
heavy rolled iron, with perforations
to alion, the air to pass through,
The
front
opening or charging
door is three fert long, and arched so a6 to be
one foot high at the centre. These furnaces cost about $150, and are charged
with 240 Ibs. of ore, 120 Ibs. of coal, and 100, Ibs. pea coal as a bed. ;rhe
double f”r”aCPs
have B” opening
30 inchps square into the main flue and
are provided
with grates, of Similar ronstructio”
to those used in the Amall
furnaces,
16 feet long by 5 feet wide. The working
doors are of the same
dimensions
?s those of th? small furnaces.
The ~%.rall~ are all of firebrick
8 inches thick,
i~nd last about eight years without
repairs.
The double’
furnaces
are charged
with 64’0 Ibs. of ore, 320 of coal, 240. of pea eoa, &8
bedding.
PITo fluxes are added, the object being ta keep the charge from
becoming: impervious
to the blast, which is furnished
by four fan-blowers.
The Process last8 four hours for each charge, and considerable
attention
0” the Part 0f the workmen,
is “rcessery
to keep the cinder porous &
nvoid the cooling of the fire by an excess of blast. Each workma”
has four
fUr”aCeS U”dPI’ his CBPB, %“d “lea”8 a”d charges one each ho”,.,
The Oxide REPOT’ Passes from the furnaces
a1on.q a conducting
channel
0~er a sheet Of water,
into B cooling
tower 75 feet high and 8@ feet in
circumference
at the base. Xuch of the damp, hnpure oxide settles in thig