The bags of blanks should[24] be carried forward to the room in which
the weighing of the individual blanks is effected by Mr. Cotton’s
automaton weighing machines. Mr. Cotton’s weighing machines form
perhaps the most elegant and clever invention of modern times. They
effect the process of weighing far more accurately than man can hope
to do, and with extraordinary accuracy determine the weight of about
twenty-three blanks per minute. Peculiarly admirable as are these
machines, their perfection has been greatly increased by improvements
suggested by Mr. Richard Pilcher, who has immediate charge of those in
the Royal Mint. Mr. Pilcher, whose inventive genius is only equalled
by his desire to give to the public the benefit of his inventions,
has rendered these automaton balances serviceable to the Mint;
whereas, when they left the hand of Mr. William Cotton, they were
of great service to the Bank of England alone, for there only two
determinations, or in fact one determination is necessary. In that
institution it is required to show that the coins issued by it are not
below the legal weight for circulation, whereas the Mint must guarantee
that coins leave its works neither above nor below the limits fixed
by law: hence the necessity for the incorporation of Mr. Pilcher’s
improvements with Mr. Cotton’s beautiful invention.
[Footnote 24: See pages 42-44.]
After reading the letter of Mr. James M. Napier in the _Times_ of
September 2nd, 1869, I can but express my surprise that that gentleman
has not seen fit to acknowledge Mr. Pilcher’s modifications instead
of claiming for himself all the credit, when a part only—and that
undoubtedly an important one—is his due.
The steel engraving exhibits a view of COTTON’S automaton machine as
used in the Royal Mint, where seventeen such machines are employed.
For the purpose of illustration, the brass side of the machine has, in
imagination, been torn away, as also has the top of the machine. To
obtain the highly-finished drawing from which this engraving was made
was a matter of no ordinary difficulty, but it was accomplished by the
skill and assiduity of Mr. E. S. Gibson, to whom my thanks are due, as
well as to Mr. J. W. Lowry, for the pains he has bestowed in executing
the engraving.
The whole theory of this balance rests on the fact that the centre
of gravity and the centre of action are in one line: either being
disturbed, the balance is no longer equal. The machine gains its
motion from a shaft fixed to the ceiling of the room. Steam contained
in a boiler exists under an ever-varying pressure, arising from the
amount of work which it may be necessary for the engine to perform,
or from the irregular combustion of the fuel, as well as from other
causes. Since it is of the utmost importance that the automaton balance
should be made to maintain a uniform pace, Messrs. Napier and Sons
found it necessary to drive the shaft which gives it motion by a
small atmospheric engine, which is placed in the weighing room. It
has been found that a chamber may be kept equably exhausted of air,
if the atmosphere be admitted to it by a uniformly weighted valve.
Such a chamber—to be described presently—is used in the Mint for other
purposes, and Messrs. Napier conducted from this a pipe, by the agency
of which the atmospheric engine is worked with a far more even and
steady motion than could be obtained by steam; in fact, the exhausted
chamber becomes a regulated spring, which softens down the variations
in the motion of the steam-engine. The shaft supported by the ceiling
conveys its motion to the weighing machine by a line A, which, passing
over the friction wheels B, circulates round the stepped wheel C,
which runs loose on the shaft communicating with E. The line A is
maintained with sufficient rigidity by a weight D, which is suspended
at the end of the lever carrying the friction wheels B. The weight D
is just sufficient to insure the continuous working of the machine,
but is so light as to permit the line A to slip on C in the event of
anything going wrong in the works of the balance. When the machine
is to be set in motion, a kind of cheek is made—by screwing—to touch
the face of the wheel C, and thus, by friction, C gives motion to the
wheel E. This is an elegant mode of meeting a chance of accident, for
in the event of the weight D proving to be too heavy, any extra force
simply disconnects this cheek from the face of C, and so stops the
machine. The machine having been set in motion, E, by communication
with the wheels F, all of which are driven by it, causes the cam G to
push forward the lever H, which, terminating at I, pushes forward the
flattened continuation of I indicated by dotted lines, until it moves
a blank placed in the collar J, at the bottom of the hopper _h_, on
to the scale-pan K, which, for the sake of clearness, is isolated,
and will be seen behind the machine and under the extreme end of the
hopper. So soon as the blank coin has been placed on the scale-pan K,
the cam L lowers a lever _n_, the office of which is to permit the
opening of the forceps M, and thus to release the rod, Q, dependent
from K upon the knife-edge R. The forceps are closed by the cam L,
which raises _n_, and by it compresses an attached spring. The forceps
are intended to hold _this_ rod Q while the blank is placed on K,
because the friction caused by the placing of the blank would have a
tendency to push K from the knife-edge on which it is suspended, and
thus blunt its delicate edge. While the forceps are opened the cam N,
by its partial revolution, lifts the rod O, which is steadied in its
motion, by a pin rising from it, and entering the inverted arch _o_;
its lower extremity working into a socket on the table on which the
whole frame of the machine stands.
Towards its lower extremity the rod O will be seen to branch out right
and left, until each end passes through a kind of step in the rods Q,
indicated by P. The office of this rod is to bring the beam, from which
the rods Q are dependent, to a dead level, as well as to release both
ends of the beam by one action. At the moment that the forceps M have
released the right hand rod Q, the cam N, by O, releases both the rods
Q, by rising from the steps P, thus permitting the beam to determine
the weight of the blank placed on K. A close inspection of the steel
engraving will show that the rods Q are suspended from and rest upon
the knife-edges R of the beam S, which has a centre knife-edge T, by
which the whole mass is supported and poised. The knife-edges are
made to find their own planes or resting-places upon curved or hollow
pieces of steel, thus securing the smallest point of contact with a
certainty of the smallest amount of friction. In ordinary balances the
substance to be weighed is placed in a pan, which is on the same level
as the pan which contains the counterpoise; but in Mr. Cotton’s balance
this condition is of no consequence, so that the counterpoise rests
ultimately upon a point which is at the same distance from the centre
of action as the point upon which the matter to be weighed rests. The
counterpoise U is placed in a kind of cage, and any variation from this
standard is at once indicated, even if it reach only to the thousandth
part of a grain. By law, the weight of a coin may vary to a certain
extent from a standard weight;[25] the variation or latitude allowed
is called _remedy_, from the Latin _ad remediam_; and in weighing,
this remedy is taken advantage of by a contrivance much simplified by
Mr. Pilcher. The weight of a sovereign is 123·274 grains, but it may
by law be either 123·474 grains, or it may fall to 123·074[26] grains.
Mr. Pilcher therefore reduced the counterpoise to the minimum allowed,
thus avoiding the placing of a remedy-wire for the light side; and he
then made the remedy-wire _q_ (shown in the first enlarged portion on
the left-hand side of the steel engraving), which is placed on the
stand W, upon a peculiarly-formed point indicated by V, so heavy that
any blank which would not raise it and the counterpoise must be within
the remedy on the _heavy_ side. In accordance with this arrangement,
the continuation of the rod Q is terminated by a cage at V; so that
if a blank be so _light_ as to be unable to raise the counterpoise U
until the stirrup comes in contact with the remedy, it is too light
to make a legal coin. This fact being determined, the motion of the
machine causes the cam X to bring back the rod I (indicated by dotted
lines), that it may be ready when required to push forward another
blank, and the forceps M to grasp the rod Q, while the cam Y permits
the falling of the rod Z, which is nearly counterpoised by the ball _m_
(the precise length of the rod being regulated by the screw _j_), until
its finger _a_ rests upon the indicator _b_. The depth to which _a_
shall fall is fixed by the step _l_ (shown by Q in the second enlarged
portion of the steel engraving). This is, of course, determined by the
forceps, securing Q at the position indicated by the weight of the
blank. The indicating finger _b_ having come to rest, the continued
motion of the machine causes the cam _c_ to permit the shoot _d_ to
fall until one of its steps _e_ comes into contact with the indicating
finger, when the lower part of the shoot must be exactly over, and
form part of, one of the tubes _k_, which terminate in boxes labelled
respectively “heavy,” “light,” “medium.” The shoot having taken its
position, the continued motion of the machine causes the cam G to
induce the placing of another blank on the scale-pan K, and this blank,
by advancing, pushes off the one just weighed, which, falling into and
through the shoot, passes to the compartment reserved for it. Suppose
the newly-placed blank to be too heavy for forming a legal coin, the
same operation goes on, but it now lifts not only the counterpoise, but
also causes the stirrup at V to lift the remedy-weight _q_. This is a
most delicate operation, for if a blow, however light, be given, it
would cause unsteadiness in the beam. Mr. Pilcher therefore determined
to make the carriage W, which supports the remedy-wire _q_, stand upon
micrometer screws, by which the remedy-wire is made just to touch the
stirrup, without pressure, while it also rests upon the most minute
points, formed by cutting away every part of V which is not actually
required—in fact, shelving it out. The scale-pan K is protected from
draught by the lantern _f_, while the blanks are directed into the
collar J by the guard _g_, as they slide down the hopper _h_, which
at its centre is supported by an upright, _i_. The blocks _p_ are the
supports which hold all the machinery to the roof of the machine.
[Footnote 25: See pages 71-73.]
[Footnote 26: See pages 73, 123, 124.]
Some new machines have recently been supplied to the Mint by Mr. James
Napier, but it is not certain that these are cheaper than the old ones.
That they are lower in price may be admitted, and they are certainly
more convenient in use, from the fact that the wheels shown at F are
placed at the back. It is, however, to be regretted that Mr. Napier
did not introduce into these new machines the recent inventions of Mr.
William Bradshaw, which are supremely simple, and, now that they are
effected, one cannot but wonder that so many minds having been engaged
on these machines, improvements such as these have not earlier seen the
light. To Mr. Bradshaw, particularly, great credit is due, for he was
obliged to overcome, not only innate difficulties, but difficulties of
position, and these latter were of no mean kind. It is to the credit of
the Mint authorities that they finally adopted these improvements, and
ordered the necessary alterations to be made in _all_ the machines.
Mr. Bradshaw’s improvements enable the automaton balances to weigh 30
per cent. more coins in the same time; yet they permit each coin to
occupy a longer space of time in being weighed. This would appear to
be a mechanical contradiction, but if reference be made to the plate
it will be seen that the cam G pushes forward the lever H, which
ultimately, by the slide, pushes the blanks on to the scale-pan K.
By altering the shape of the cam G, Mr. Bradshaw causes it to do its
work more rapidly, and thus leaves the piece on K longer than before;
but that this time may not be lost, he alters also the shapes of the
cam L and of the cam N, so that the forceps M are opened, and the beam
is released more rapidly: thus the balance would be longer in action;
but to utilise the time ready to be saved, he alters also the driving
pulley E, causing the machine to make 30 per cent. more determinations
per minute, and that this may be effected with greater certainty he
reduced the depth of the step, shown at _e_, to just one-half, so that
the beam has to travel only half the distance it formerly travelled to
determine the position of the light, heavy, or medium piece. He next
proceeded to alter the rod O, because he observed that it received a
tilting motion arising from its being lifted by a shoulder, as shown
in the plate. To overcome this defect he made the rod straight up to
a certain point, where he divided it into a kind of loop which passed
over the cam N, which, as it revolves, lifts this rod perpendicularly.
He still found that the cam N had a tendency to push this rod against
its bearings, especially at _o_, so he placed a spring of brass between
the top of its loop and the cam N, and secured at one end to _p_, and
by this contrivance made the cam to lift the brass, and that in its
turn to raise the rod O. There was yet another difficulty, caused by
an occasional stoppage of the action of the spring which softens the
descent of the bearing of the rod O into its lower socket; this he
removed by cutting a hole in the side of the socket, so that it can be
seen at once if the spring be in action. I am not one who approves his
suggestions as to the remedy-wires. These may be the means of saving
time, but they are wrong in principle, and I do not describe them.
Great inconvenience arose from the collection of dust, spangles of
bullion, and other foreign matter on parts of the balance. This Mr.
Bradshaw overcame by two simple contrivances; first, he pierced the
bottoms of the grooved trays, so that these substances might in a great
measure fall through while the blanks were being arranged in rouleaux,
thus separating the largest pieces, which, falling down the shoot,
would stop its action; and, secondly, he placed a glass shelf midway
between the table and the beam, that is, beneath the hopper _h_, where
it terminates at J, and above the beam S, where it is seen near the
forceps M, thus protecting the beam and forceps. These may appear to
be trifling alterations,—they are nevertheless to Cotton’s balance
what the compound metal balance-wheel is to a watch. Mr. Pilcher was
granted the _magnificent_ sum of £40 for his invention of the file (to
be described), but it is hoped that Mr. Bradshaw will be rewarded with
a far more open-handed generosity; for if, by judicious liberality,
encouragements are offered to those in the Civil Service to give to
the country the benefit of their inventions, we may still hope that
even our Government institutions will bear comparison with ordinary
commercial manufactories as regards the development of inventive
genius. Nor is this a small matter, for all the working improvements in
the Cotton’s balance have been made by those whose duty it is to attend
to their working; yet I am not aware that any acknowledgment, either
direct or indirect, has been made to the officers concerned. It is
said that their salaries cover all their time and energy. This may be
true, but such a policy is not calculated to result in many great steps
towards perfecting either machines or processes.
It is well to state that the beam in Mr. Cotton’s balance is 8·90
inches in length, and that its weight is 288·41 troy grains.
Those blanks which are neither too light nor too heavy are called
_medium_, and are weighed and put into bags for future issue as coins.
The _light_ are reserved for the melting-pot. The _heavy_ blanks should
be reduced by means of a peculiar kind of file to the weight of medium
blanks, and thus saved from being melted, so avoiding further loss
to the Mint. This file was invented by Mr. Pilcher, who, being the
officer of this room, considers his duty to be neglected if there be
any improvement capable of being made, but which is left undone; he
never tires till the invention is complete and the machine made. Mr.
Albert Barre, the distinguished engraver to the Paris Mint, declares
this file to have surmounted all the difficulties he has met with in
this part of the process. In his own words, “it leaves the face of the
blank untouched, and free to develop the work of the engraver, which no
other file does, or can effect, because any metal which is _ploughed_
out from the face of a blank, leaves a hole which is not filled up in
coining.”
The opinions which I have here expressed have so far prevailed on two
of the travellers to European Mints, as to induce them to glance,
though rather shyly, at the necessity for reducing heavy blanks; but
Mr. Napier writes a passage which I quote, as it demonstrates that
he, who is admittedly one of the most successfully ingenious men of
the age, has thought over and studied the words I wrote at page 60 of
the last edition—he took that book in his hand to the Mint on the day
after its publication—with that attention to which he thought they were
entitled. I beg the reader to ponder over Mr. Napier’s words, they are
most important; but I hope those who will be called upon to vote the
necessary money will also read my remarks on this extract from Mr.
Napier’s report on European Mints. He says at page 44:—
“_Treatment of Too-heavy Blanks._—Notwithstanding the
employment of the best mechanical appliances for rolling
the bars, adjusting the fillets to gauge, and cutting
out the blanks, and the most intelligent and painstaking
workmen to carry on the operations, still, owing to
unavoidable imperfections in the means, the blanks, when
cut from the fillets, will not be found equal in weight,
nor, indeed, so nearly equal that they can be recognised as
of equal value, and passed on to be manufactured into coins
destined to be put into circulation, and to represent one
value. The irregularities will necessarily be more or less,
according to the care and ability of the workmen, and the
condition of the machinery; but under the most favourable
circumstances only a certain proportion of the blanks
will be found to come within the limits which it has been
considered desirable to set down to restrict the quantity
of error.
“This being so, the following questions present themselves:
Are the too-heavy and too-light blanks to be returned to
the crucible and remelted, or to be passed on and detected
only in the finished coin, and then sent to the crucible?
Or are too-light blanks to be avoided altogether, and
all the blanks to be made either of sufficient weight or
too heavy? and in such case are the too-heavy blanks to
be submitted to some process for reducing their weight
to within the legal limit? Or is a more exact means to
be preferred, by which they will be equalised to that
perfection which cannot practically be questioned, and by
which they will become, for all purposes, one and the same
weight?
“The facts collected are, that at nearly all the European
Mints the reduction of too-heavy blanks, both of silver
and gold, is practised, to avoid the loss attendant upon
their return to the crucible, and that the endeavour is
to make all the blanks either standard weight or heavier,
so as to admit of reduction, to err, indeed, on the heavy
side, even to the extent of necessitating the reduction
of all the blanks. So great is the importance generally
attached to this department, that it is calculated that, in
some instances, nearly as many hands are employed in the
service of it, including the weighing, as in all the other
working departments combined. In Berlin, where particular
care is devoted to the weight of the coins, between 200 and
300 men are employed in times of pressure in the weighing
and equalising of the blanks, which operations are in this
instance performed by the workman with a hand shaving
apparatus, fixed to the table at which he sits, and a pair
of scales also placed near to him. The work done by one man
is revised by a second, and the file is used for giving the
finishing touch, so that the blanks are brought to great
perfection in weight. But although the extent of the means
shows the great importance attached to the results in the
establishments visited, and the large expenditure which, at
least in the opinion of the directors of these Mints, may
be permitted with profit in this department, the serious
consideration of the employment of so many hands would
militate against the carrying out of the system in the New
Mint. It may be satisfactory, therefore, to know that,
in case the desirability of an exact coinage should be
entertained, means for assuring it are at hand without the
employment of manual labour for the purpose. The subject
has, indeed, for many years occupied attention, and,
after much labour and expense, the difficulties have been
overcome, and a machine has been constructed to the order
of the Government of India which fulfils all the required
conditions for equalising the coinage to that perfection
that no appreciable difference need exist between the
standard weight and the coin blank which has passed through
the machine. This machine differs essentially from those
employed at the Mints visited, and which, it has been
explained, only take a fixed quantity off each blank
presented to the cutting tool, without reference to the
weight of the blank, the operation being repeated or not,
according to the result; or, in other words, no matter what
be the weight of the blank, whether nearly light enough, or
much too heavy, the cutting tool of the machine treats all
in the same manner.
“The equalising machine referred to, on the contrary, not
only takes from the too-heavy blanks, each in succession,
a quantity of their surplus weight, but it ascertains how
much it is necessary to take off each blank to reduce it
to the standard weight; and it deducts that amount only;
so, although the blanks which are supplied to the hopper,
or reservoir of the machine, enter the machine of unknown
weight, they are equalised by it in once passing through,
and are delivered into a receptacle for the finished work,
all of one weight, the standard, or so near to it that good
ordinary scales, such as are used for weighing blanks and
coins, will not detect a difference.
“Means can therefore be provided for the purpose, should it
be decided to reduce the blanks to equal weight, or only
to within the pale of accuracy instituted by Parliament,
the basis of which legislation must be taken to have been
the then practicable approach to perfection; for it is
to be presumed that, with a sufficient assurance that
accuracy akin to perfection was attainable ALONG WITH
ECONOMY, the wisdom of Parliament would have enacted
accordingly.
“The first outlay for self-acting coin blank equalising
machinery WOULD NECESSARILY BE LARGE, but it
is believed at the same time that the saving would be
considerable, especially upon gold.
“The question of the amount of economy would have to be
more fully gone into, and the expense of the machinery
accurately estimated. Extensive and continuous experiments
with the machine have also STILL TO BE MADE TO ACQUIRE
A KNOWLEDGE OF ITS USE, and to ascertain, after a
_lengthened_ probation, whether any modifications in
the details are advisable: the limited experiments already
made leave no doubt, however, of the successful result.
“The arguments in favour of an _exact coinage_ chiefly
rest upon an economical basis, and branch out beyond the
walls of the establishment into questions of currency,
wear, and recoinage, which it is not thought necessary to
treat of here; at the same time it may be stated that it
seems desirable that the coinage should be made as exact to
weight as possible CONSISTENT WITH ECONOMY, and
that an _exact coinage_ would be found more economical
as a circulating medium, would be more just, and a better
starting-point from which to legislate for the withdrawal
from circulation of worn coin than a coinage issued from
the Mint with acknowledged errors, or differences in weight
so substantial as to be represented in value, in the case
of gold coins, by some of the lesser denominations of the
coins of the realm.”
The reasons which Mr. Napier gives are worthy of grave
consideration—they are mine wholly—except so far as regards those to
which I have drawn attention by printing them in small capital letters,
and which show that even with his vast experience he dare not answer
for the success of his machine, while the suggestion of the necessity
“to acquire a knowledge of its use” should make a desire to recur to a
successful machine paramount. If, indeed, I rested on my own opinion,
I should be content to see Mr. Napier’s machine tried, although I
think its failure would be established; but it so happens that I can
quote the opinion of the late Master of the Mint on the machine under
consideration, expressed at a period when the efficiently economical
conduct of the Royal Mint had received his utmost consideration. In his
letter to the Treasury, dated 7th June, 1860, he says:—
“I may be allowed to call to your recollection that a
Parliamentary grant of £1,100 was obtained by the Mint in
1856 for the purchase of two automaton filing and adjusting
machines, which it was proposed to have constructed by
Messrs. R. Napier and Sons, the eminent engineers. No part
of this grant has been appropriated. The rapid amendment in
the blanks which took place immediately afterwards led me
to suspend the order for these machines, and ultimately to
abandon the idea of any great expenditure for the object
contemplated. In the meantime also, a machine of a much
more simple character was contrived by Mr. R. Pilcher, of
the weighing room, and was constructed in the Mint, with no
assistance from without. Pilcher’s adjusting machine has
proved sufficiently effective, costs nothing for labour,
and has now been in constant operation for two years. The
cost of making a pair of machines such as we now possess
is estimated at £60, a sum which was saved to the public
by the mode in which the work was executed. Trusting that
the Lords Commissioners of her Majesty’s Treasury will be
disposed to consider favourably the merit and practical
value of such an invention, I venture to solicit their
Lordship’s sanction to the application of £60, the sum
just stated, to the benefit of the inventor, jointly with
an ingenious mechanic on the establishment, who gave
material assistance in the construction of the machine. I
would propose the following awards, if agreeable to their
Lordships:—To Mr. R. Pilcher, £40; to Meredith Jones, £20.”
It was upon advice tendered by myself that Mr. Graham thus excluded
the machine now recommended by Mr. Napier. I maintain that a simple
machine should be preferred before a complicated one, and the Mint
authorities should give Mr. Pilcher’s £60 machines—admittedly perfect
in operation—a fair trial against Mr. Napier’s £1,100 machines, and see
if they prove _equally effective_. If, on the other hand, Mr. Napier’s
fails, then it is but fair to the public that that machine which is
undoubtedly a success, and for which the inventor has been _publicly
rewarded, although in a most inadequate manner_, should be used.
The machine thus spoken of was used with the utmost advantage until
1866, when its use was abolished by the advice of Mr. John Graham, who
subsequently, in 1868, broke it to pieces that _his improvements_ might
be rendered permanent, thus causing an expense of 50 per cent. on the
total cost of manufacture for _rejected coins_,[27] because the use
of the file having been abolished, the coined money alone was weighed,
thus rendering it impossible to reduce the heavy pieces.
[Footnote 27: That is, coins which, although otherwise perfect in
manufacture, are not within the limited variations of weight permitted
by the Mint regulations.]
[Illustration: Fig. 14.—Pilcher’s Filing Machine.]
Although the use of this file has thus been stopped, it is greatly to
be hoped that it will again be employed, and thus enable the Government
to produce coined money at the cheapest possible[28] rate, because it
enables the Mint authorities to obtain the largest per-centage from the
bars. Feeling that this much-desired re-introduction will take place,
it is thought wise to give the following description of Pilcher’s file,
which, if not desired for the benefit of our own Mint, will be adopted
by other coining countries:—Fig. 14 is a representation of this compact
machine. The blanks A are placed in rouleaux in a tube B, which is open
at top and at bottom; through the opening at the bottom the blanks rest
their EDGES on the file C, which, as it revolves about 1,000 times per
minute, files off metal from the edge of the blank. Each machine has
two tubes, and when both have been filled the rod D, which carries a
triangular knife-edge, is released by the lever E, and the knife-edge
resting upon the upper edge of the blanks A,—with the intention of
offering resistance to their rotary motion,—enables the operator to
remove MUCH OR LITTLE metal from their edges at pleasure by increasing
the resistance which D offers by adding a weight G on to the gallery F.
H is a glass dish into which the dust, as it is removed from the edges
of the blanks, falls, thus insuring a perfect _separation of the dust_
from the blanks. The blanks in B are kept in their position by small
blocks of ebony, which are secured by the thumb-screws I. Motion is
given by the wheel J, which communicates with the pulley K by a cord or
catgut. The whole machine stands on a block of mahogany L, secured to a
table of oak. M is a screw which is used to tighten the cords between J
and K. Between C and H is a hopper of brass to catch flying particles
of the precious metals. Each file reduces 250 sovereign blanks per
minute.
[Footnote 28: See pages 108, 109.]
The objections which were raised to the introduction and use of this
machine were curious, and amongst others it was firmly maintained that
it caused the coining press to make brockages, because the blanks which
had been filed were smaller than those which had not been thus treated.
The amusing part of this objection was that _all_ the blanks were
afterwards reduced to a uniform diameter by the edges being compressed
_before_ being coined.
The medium blanks—now unfortunately the coined moneys—are rung by boys
to detect any which may be dumb or cracked, and which are rejected for
melting. Dumb or cracked pieces arise when bubbles of air are enclosed
in the bars at the time of pouring the fluid metal into the moulds in
the melting-house.
Besides this source of dumb work may be mentioned another of large
occurrence in silver, and occasionally met with in gold, which results
from an imperfect mixture of the alloy at the time of melting, and
developes itself at the draw-bench, where whole fillets, of six feet
long, may be seen to separate into two complete layers of metal, the
inner surfaces being coated with a thin film of copper, frequently
quite pure, but sometimes in the form of suboxide. It would thus appear
that a globule of copper becomes enveloped in a volume of fluid gold
or silver, and, in the act of pouring, this globule is drawn out into
a kind of wire, perhaps extending some inches in length, enclosed in
precious metal. When this is rolled it is all flattened together, but
there is no adhesion between the surfaces, so that when the fillet
passes through the draw-bench the lateral motion given to the atoms
of the metal causes the slip which finally separates the two surfaces
of metal, and the eye at once detects the existence of the fault. In
the coinage of 1857, no less than 141·38 ounces of gold fillets thus
imperfect were returned to the melter in one day, and on the whole of
that coinage these fillets averaged nearly 0·50 per cent. (see page
92). In the case of silver this defect is of less consequence, but
of greater occurrence. It is the duty of the melter to see that such
bars are neither produced nor forwarded, and there can be but little
doubt that in a properly conducted Mint the melter would be directed to
re-melt such fillets without payment to the men.
[Illustration: Fig. 15.—Jones’s Edge-Compressor.]
The medium blanks which would now be fit for coining should be weighed
up in bags of about 500 ounces, instead of 180 ounces, as is the
custom, and sent forward to the room in which is placed a machine which
has to diminish the diameter of each blank by compressing its edges.
This is called a _marking machine_, but such a name being obviously
improper, it is preferred to call it the EDGE-COMPRESSOR. Up to 1861
the best machine for this purpose was that invented and patented by
Messrs. R. Heaton and Sons, of the Mint, Birmingham; but in the early
part of 1858 the subject of the varying diameter of blanks came under
consideration as effecting the production of brockage. Mr. Pilcher was
consulted by me, and proposed a machine, of which he gave the outline,
which I submitted to the Master of the Mint on the 31st of March, 1858.
This machine was to be fed from the top, but was abandoned because
it did not meet the desired minimum of 1,000 pieces per minute. Mr.
Pilcher therefore proposed to erect on the same spindle five revolving
discs, and to face these five discs with as many cheeks. At a given
time it was determined to manufacture a marking machine, and one of
five which Mr. Pilcher proposed was to be made. It was preferred to ask
Mr. Meredith Jones to assist in its manufacture. Mr. Jones had also
a design for a machine for this purpose, and it was arranged that as
Mr. Jones made Mr. Pilcher’s file he should make his own machine. Mr.
Jones proposed, and Mr. Pilcher accepted, the following proposition.
Mr. Pilcher was to retire from the machine, and in consideration of
his so retiring, and allowing the machine to be called Jones’s marking
machine, Mr. Jones was to give Mr. Pilcher one-half of whatever
sum might be paid by the Mint for the use of the machine. Fig. 15
represents Mr. Jones’s machine. The blanks are placed in the hopper
A, and fall by an incline into a tube B until they rest at C, on a
notched wheel D. As D revolves each of its notches carries away the
bottom blank of the pile from the tube B, and leaves it to slide down
the tube E till it reaches the block F. The block F is cut with a
narrow groove, which exactly corresponds with the groove Gᵃ on the
plate or disc G. The disc G revolves, and as the blank slides down and
comes with some little impetus against the groove in the block F, the
groove Gᵃ catches it, and causes it to take two revolutions between
the disc G and the block F, finally permitting its escape at H, when
it falls into I, being now reduced in diameter and thicker on the
edge, but its centre remaining as it was before. The machine is driven
by J, the shaft of which carries a reduced rigger for the driving of
K. The hopper is supported by the rod L. The distance between F and
G represents the diameter of the blank after its edge is compressed,
this distance being determined by the screws seen at M. Blanks of all
diameters may be compressed at this machine if the block F and the
plate or disc G be removed and replaced by others, neither operation
taking many minutes. The edges of the blanks are compressed at the rate
of 700 per minute. A boy of fourteen could work this perfectly well,
and with more convenience now that the hopper is replaced by such a one
as is used to supply Mr. Cotton’s weighing machine. The edge of the
blank is compressed with a view to prepare it for the _crenating_ to be
given by the collar in the after process of conversion into a coin.
The blanks are conveyed from the edge-compressor to the annealing room,
where they are placed in rouleaux in iron boxes, the tops of which are
luted on with clay, the boxes are then placed on iron carriages, and
run into reverberatory furnaces, heated by Juckse’s smoke-consuming
apparatus, where they remain for an indefinite period. The furnaces are
like that represented in the rolling room for annealing the fillets in
copper tubes. To anneal the blanks, the temperature should be raised
rapidly until the boxes attain a full red heat; and the time allowed
for the operation should be from twenty to twenty-five minutes at the
utmost. After the heating, the boxes are withdrawn from the furnace
and placed on the floor of the room, till the blanks are assumed to
have become of a low red or black heat, the point below that at which
copper combines rapidly with oxygen; they are then opened. If the boxes
be opened while the blanks are still of a full red heat, there is what
is called too much loss by annealing, or, in other words, too much
of the copper has become oxidised, and thus rendered soluble in the
dilute sulphuric acid into which they are presently removed. The box
having been opened, the blanks are turned out into a copper tray, and
on this carried to a cistern of cold water, in which a colander stands;
they are thrown through the water into this colander, and thus cooled
rapidly. When cool, they are taken in the colander to a leaden cistern
of nearly boiling dilute sulphuric acid, into which they are placed,
and allowed to remain for about three or four minutes. By means of this
bath of sulphuric acid a thin skin of oxide of copper is removed; the
gold on the surface from which the copper has been washed out is of
a sponge-like form, and gives a beautiful bloom to the new coin when
it is struck. This process is called _blanching_, and is of great
interest to the coiner, as it is here that his loss by coining takes
place. The bars of gold sent to the coiner are found to be standard
within certain limits,[29] therefore the blanks produced from those
bars must be of the same fineness; but by this process of blanching,
copper is removed; hence the standard, or the amount of pure gold
contained in the blanks, is proportionably raised, and this tells on
the million to an amazing extent. When the annealing is conducted for
too long a period, the copper becomes oxidised to too great an extent
during the time of annealing, for there is no atmosphere more capable
of oxidising than is that of one of these furnaces; it is for this
reason that the heat should be gained rapidly, before that oxidising
atmosphere shall have time to permeate the luting and attack the copper
of the standard gold. At the trial of the pyx in 1861 the gold coined
by Mr. Thomas Graham, the late Master, was found to be “4 grains on
the pound too fine;” that is to say, containing in 5,760 grains 5,284
grains of pure gold in the place of 5,280 grains, which it should have
contained. This is well for the people, but it is bad for the Master of
the Mint, because he has lost 4 grains of pure gold on each pound that
he has coined, which amounts to no less than £757·65870 in value upon
every million of sovereigns. This loss may well be avoided, either by
adding extra alloy to allow for this removal of copper, or, as would be
far wiser, by abolishing the process of annealing the blanks, as was
done in 1859, when more than a quarter of a million of sovereigns were
coined from unannealed blanks obtained from brittle gold which was much
harder than any ordinary gold to be met with. It must be remembered
that the saving of bullion would leave a large margin for the increased
destruction of dies, and in addition the coin would wear longer in
circulation.
[Footnote 29: See page 53.]
By his elaborate experiments Mr. Charles Hatchett proved not only
that the British standard gold was the best alloy for coins, but that
this alloy should be so manipulated as to avoid either the extreme of
ductility or of hardness, and when this medium was attained the coins
produced wore longer and better than any others.
It will be of importance in this place to consider the question of
annealing the blanks previously to coining them, and experience teaches
that this process should be omitted. The gold alluded to as coined in
1859 from unannealed blanks was the same gold that was spoken of as
being so toughened in the form of bars when the fluid metal had been
poured through a stream of coal gas.[30] The gold contained antimony,
arsenic, and lead, so was predisposed to become brittle; but by pouring
through the air it absorbed oxygen, and became certainly the most
brittle gold that has passed through my hands. It was toughened by
reducing the oxide of copper, and worked remarkably well, producing
the most workable fillets, regular and uniform blanks, which yielded
an average of 5·67 per cent. rejected. The blanks were tough, soft,
and very malleable, capable of being cut with a chisel without
fracture, and ringing musically on an iron block, thus satisfying
all the requirements of good coining gold; but directly these blanks
were annealed they showed 30 per cent. of pieces so brittle that they
could be broken by a moderate pressure of the finger and thumb. After
coining, the whole mass became so brittle that less than 2 per cent.
remained sound after twice ringing on an iron block, as is the usual
practice. These brittle coins, when again annealed, and suddenly cooled
by plunging into cold water, became tolerably tough, and withstood
ringing to 8 times, when they again became brittle. It now became
evident that none of this gold should be issued to the public,—indeed,
I may state that this same gold had been rejected by all the coining
countries as unfit for coin. It was therefore ordered to be melted
and returned to the Bank as unfit for coin, its value being £167,539.
After every possible obstacle had been placed in the way, I overcame
the aversion to change, obtained permission to try some experiments
on this gold, rewrought it, and coined it all without annealing. The
coin thus produced was so tough that an ordinary man could not break
a sovereign even by the aid of a pair of pliers.[31] Yet when these
toughened coins were annealed, they became so brittle that a child
could break them readily. In the Royal Mint some of these coins in each
state are preserved. Mr. Graham, then ever anxious to secure to the
Mint any advantage, was pleased to address to the Treasury a letter on
the subject of this gold, in which he said, “A correspondence between
the Governor of the Bank and myself on the brittle property of the gold
occasionally imported into the Mint to be coined was formerly brought
under your notice in my letter of the 21st March, 1857. The evidence
of the evil in question was not confined to the Royal Mint, but has,
I believe, been felt at all other mints, and also by goldsmiths
generally, since the recent gold discoveries. It was traced to the
presence in the gold of a minute portion of antimony or arsenic (often
not greater in quantity than one-tenth of a per cent.), which escapes
the observation of the assayers. But no remedy in dealing with such
gold then presented itself, except the expensive one of having the
brittle gold refined.
[Footnote 30: See page 6.]
[Footnote 31: These coins, struck between marked dies, may be
recognised by a small line which I placed in the centre of the ribbon
at the back of the head representing her Majesty on the obverse.]
“An unusually large proportion of the gold received for coining
last year was of this defective character, but the whole of it was
successfully coined notwithstanding, and no part returned to the Bank
to be refined, as on former occasions.
“This improvement in the practice of the coining department is the
result of a laborious investigation made in the coining department, of
which I am happy to assign the chief merit to Mr. Ansell.
“It now appears that the antimony or arsenic acts injuriously when
the gold blanks are allowed to cool gradually, but not when cooled
suddenly, after annealing, the gold appearing to have time to
crystallise and become granular under the influence of the antimony
particles in the one case, but not in the other. The improvement may be
justly represented as one of considerable value. It saves entirely much
extra labour hitherto applied to brittle gold without any beneficial
result. It will also lead to the diminution of waste, of which brittle
gold was always a fruitful source.”[32]
[Footnote 32: Besides many verbal congratulations, the Master wrote me
the following letter:—
Registered No. 3026, 1860.
Royal Mint, 20th October, 1860.