1. The _bucker_, or beater, formed of a cast-iron plate, 3 inches
square, with a socket in its upper surface, for receiving a wooden
handle. In the neighbourhood of Alston Moor, crushing cylinders have
been substituted for the beating bucker; but even now, in Derbyshire,
buckers are generally employed for breaking the pieces of mixed ore,
called _knock-stone-stuff_.
At the mines of this county, the _knocker’s_ workshop, or _striking
floor_, is provided either with a strong stool, or a wall 3 feet high,
beyond which there is a flat area 4 feet broad, and a little raised
behind. On this area, bounded, except in front, by small walls, the ore
to be bruised is placed. On the stool, or wall, a very hard stone slab,
or cast-iron plate is laid, 7 feet long, 7 inches broad, and 1-1/2
inches thick, called a _knock-stone_. The workmen seated before it,
break the pieces of mixed ore, called _bowse_ in Derbyshire, with the
bucker.
_Crushing machines_ are in general use at Alston Moor, to break the
mingled ores, which they perform with great economy of time and labour.
They have been employed there for nearly forty years.
[Illustration: 628 629]
This machine is composed of one pair of fluted cylinders, _x x_, _fig._
628., and of two pairs of smooth cylinders _z z_, _z z_, which serve
altogether for crushing the ore. The two cylinders of each of the three
pairs turn simultaneously in an inverse direction, by means of two
toothed wheels, as at _m_, _fig._ 629., upon the shaft of every
cylinder, which work by pairs in one another. The motion is given by a
single water wheel, of which the circle _a a a_ represents the outer
circumference. One of the fluted cylinders is placed in the prolongation
of the shaft of this wheel, which carries besides a cast-iron toothed
wheel, geered with the toothed wheels _e e_, fixed upon the ends of two
of the smooth cylinders. Above the fluted cylinders, there is a hopper,
which discharges down between them, by means of a particular mechanism,
the ore brought forward by the waggons A. These waggons advance upon a
railway, stop above the hopper, and empty their contents into it through
a trap-hole, which opens outwardly in the middle of their bottom. Below
the hopper there is a small bucket called a shoe, into which the ore is
shaken down, and which throws it without ceasing upon the cylinders, in
consequence of the constant jolts given it by a crank-rod _i_ (_fig._
629.) attached to it, and moved by the teeth of the wheel _m_. The shoe
is so regulated, that too much ore can never fall upon the cylinders,
and obstruct their movement. A small stream of water is likewise led
into the shoe, which spreads over the cylinders, and prevents them from
growing hot. The ore, after passing between the fluted rollers, falls
upon the inclined planes N, N, which turn it over to one or other of the
pairs of smooth rolls.
These are the essential parts of this machine; they are made of iron,
and the smooth ones are case-hardened, or _chilled_, by being cast in
iron moulds. The gudgeons of both kinds move in brass bushes fixed upon
iron supports _k_, made fast by bolts to the strong wood-work basis of
the whole machine. Each of the horizontal bars has an oblong slot, at
one of whose ends is solidly fixed one of the plummer-blocks or bearers
of one of the cylinders _f_, and in the rest of the slot the
plummer-block of the other cylinder _g_ slides; a construction which
permits the two cylinders to come into contact, or to recede to such a
distance from each other, as circumstances may require. The movable
cylinder is approximated to the fixed one by means of the iron levers X
X, which carry at their ends the weights P, and rest upon wedges M,
which may be slidden upon the inclined plane N. These wedges then press
the iron bar O, and make it approach the movable cylinder by advancing
the plummer-block which supports its axis. When matters are so arranged,
should a very large or hard piece present itself to one of the pairs of
cylinders, one of the rollers would move away, and let the piece pass
without doing injury to the mechanism.
Besides the three pairs of cylinders which constitute essentially each
crushing machine, there is sometimes a fourth, which serves to crush the
ore when not in large fragments, for example, the _chats_ and _cuttings_
(the moderately rich and poorer pieces), produced by the first sifting
with the brake sieve, to be presently described. The cylinders composing
that accessory piece, which, on account of their ordinary use, are
called _chats-rollers_, are smooth, and similar to the rollers _z z_,
and Z´ Z´. The one of them is usually placed upon the prolongation of
the shaft of the water-wheel, of the side opposite to the principal
machine; and the other, which is placed alongside, receives its motion
from the first, by means of toothed wheel-work.
The _stamp mill_ is employed in concurrence with the crushing cylinders.
It serves particularly to pulverize those ores whose gangue is too hard
to yield readily to the rollers, and also those which being already
pulverized to a certain degree, require to be ground still more finely.
The stamps employed in the neighbourhood of Alston Moor are moved by
water wheels. They are similar to those described under TIN.
_Proper sifting or jigging apparatus._--The hand sieve made of iron wire
meshes, of various sizes, is shaken with the two hands in a tub of
water, the _ore vat_, being held sometimes horizontally, and at others
in an inclined position. This sieve is now in general use only for the
_cuttings_ that have passed through the grating, and which though not
poor enough to require finer grinding, are too poor for the brake sieve.
When the workman has collected a sufficient quantity of these smaller
pieces, he puts them in his round hand sieve, shakes it in the ore vat
with much rapidity and a dexterous toss, till he has separated the very
poor portions called _cuttings_, from the mingled parts called _chats_,
as well as from the pure ore. He then removes the first two qualities,
with a sheet-iron scraper called a _limp_, and he finds beneath them, a
certain portion of ore which he reckons to be pure.
The _brake sieve_ is rectangular, as well as the cistern in which it is
agitated. The meshes are made of strong iron wire, three-eighths of an
inch square. This sieve is suspended at the extremity of a forked lever,
or brake, turning upon an axis by means of two upright arms about 5 feet
long, which are pierced with holes for connecting them with bolts or
pins, both to the sieve-frame and to the ends of the two branches of the
lever. These two arms are made of wrought iron, but the lever is made of
wood; as it receives the jolt. A child placed near its end, by the
action of leaping, jerks it smartly up and down, so as to shake
effectually the sieve suspended at the other extremity. Each jolt not
only makes the fine parts pass through the meshes, but changes the
relative position of those which remain on the wires, bringing the purer
and heavier pieces eventually to the bottom. The mingled fragments of
galena, and the stony substances called _chats_ lie above them; while
the poor and light pieces called _cuttings_, are at top. These are first
scraped off by the _limp_, next the mixed lumps, or _chats_, and lastly
the pure ore, which is carried to the _bing heap_. The _cuttings_ are
handed to a particular class of workmen, who by a new sifting, divide
them into mere stones, or second _cuttings_, and into mixed ore
analogous to _chats_.
The poor ore, called _chats_, is carried to a crushing machine, where it
is bruised between two cylinders appropriated to this purpose under the
name of _chats_ rollers; after which it is sifted afresh. During the
sifting many parcels of small ore and stony substances pass through the
sieve, and accumulate at the bottom of the cistern. When it is
two-thirds filled, water is run slowly over it, and the sediment called
_smitham_ is taken out, and piled up in heaps. More being put into the
tub, a child lifts up the _smitham_, and lays it on the sieve, which
retains still on its meshes the layer of fine ore. The _sifter_ now
agitates in the water nearly as at first, from time to time removing
with the _limp_ the lighter matters as they come to the surface; which
being fit for washing only in boxes, are called _buddler’s offal_, and
and are thrown into the _buddle hole_.
Mr. Petherick, the manager of Lanescot and the Fowey Consol mines, has
contrived an ingenious jigging machine, in which a series of 8 sieves
are fixed in a stationary circular frame, connected with a plunger or
piston working in a hollow cylinder, whereby a body of water is
alternately forced up through the crushed ore in the sieves, and then
left to descend. In this way of operating, the indiscriminate or
premature passage of the finer pulverulent matter through the meshes is
avoided, because a regulated stream of water is made to traverse the
particles up and down. This mode has proved profitable in washing the
copper ores of the above mentioned copper mines.
_Proper washing apparatus._--For washing the ore after sifting it, the
running buddle already described is employed, along with several chests
or _buddles_ of other kinds.
1. The _trunk buddle_ is a species of German chest (see METALLURGY and
TIN) composed of two parts; of a cistern or box into which a stream of
water flows, and of a large tank with a smooth level bottom. The ore to
be _trunked_ being placed in the box, the workman furnished with a
shovel bent up at its sides, agitates it, and removes from time to time
the coarser portions; while the smaller are swept off by the water and
deposited upon the level area.
2. The _stirring buddle_, or chest for freeing the _schlamms_ or slimy
stuff from clay, is analogous to the German chests, and consists of two
parts; namely, 1. a trough which receives a stream of water through a
plug hole, which is tempered at pleasure, to admit a greater or less
current; 2. a settling tank with a horizontal bottom. The metallic
_slime_ being first floated in the water of the trough, then flows out
and is deposited in the tank; the purest parts falling first near the
beginning of the run.
3. The _nicking buddle_ is analogous to the tables called _dormantes_ or
_jumelles_ by the French miners. See METALLURGY. They have at their
upper end a cross canal or spout, equal in length to the breadth of the
table, with a plug hole in its middle for admitting the water. Alongside
of this channel there is a slightly inclined plank, called _nicking
board_, corresponding to the head of the _twin table_, and there is a
nearly level plane below. The operation consists in spreading a thin
layer of the _slime_ upon the _nicking board_, and in running over its
surface a slender sheet of water, which in its progress is subdivided
into rills, which gradually carry off the muddy matters, and strew them
over the lower flat surface of the tank, in the order of their density.
[Illustration: 630]
4. The _dolly tub_ or rinsing bucket, _fig._ 630., has an upright shaft,
which bears the vane or _dolly_ A B, turned by the winch handle. This
apparatus serves to bring into a state of suspension in water, the fine
ore, already nearly pure; the separation of the metallic particles from
the earthy ones by repose, being promoted by the sides of the tub being
struck frequently during the subsidence.
5. _Slime pits._--In the several operations of cleansing ores from mud,
in grinding, and washing, where a stream of water is used, it is
impossible to prevent some of the finely attenuated portions of the
galena called _sludge_, floating in the water, from being carried off
with it. _Slime pits_ or _labyrinths_, called _buddle holes_ in
Derbyshire, are employed to collect that matter, by receiving the water
to settle, at a little distance from the place of agitation.
These basins or reservoirs are about 20 feet in diameter, and from 24 to
40 inches deep. Here the suspended ore is deposited, and nothing but
clear water is allowed to escape.
The workmen employed in the mechanical preparation of the ores, are
paid, in Cumberland, by the piece, and not by day’s wages. A certain
quantity of crude ore is delivered to them, and their work is valued by
the _bing_, a measure containing 14 cwt. of ore ready for smelting. The
price varies according to the richness of the ore. Certain qualities are
washed at the rate of two and sixpence, or three shillings the bing;
while others are worth at least ten shillings. The richness of the ore
varies from 2 to 20 bings of galena per _shift_ of ore; the shift
corresponding to 8 waggons load.
1. The cleansing and sorting of the ores are well performed in
Cumberland. These operations seem however to be inferior to the
cleansing on the _grid steps_, _grilles à gradin_, of Saxony (see
METALLURGY), an apparatus which in cleaning the ores, has the advantage
of grouping them in lots of different qualities and dimensions.
2. The breaking or bruising by means of the _crushing machine_, is much
more expeditious than the Derbyshire process by _buckers_; for the
machine introduces not only great economy into the breaking operation,
but it likewise diminishes considerably the loss of galena; for stamped
ores may be often subjected to the action of the cylinders without
waste, while a portion of them would have been lost with the water that
runs from the stamp mill. The use of these rollers may therefore be
considered as one of the happiest innovations hitherto made in the
mechanical preparation of ores.