Ma. GmL, on a French Method o f S t r i k ing Medallions. 3

atmospheres~ two-thirds up the tube, and small globules of liquid began to form about the fop of it; at lfl00 atmospheres .the qui¢l~Si!;- vet remained three-fourths up the tube, and a beautiful transparen~ liquid Was seen on the surface of the quicksilver, in quantity about ~a-x l)art of the column o f air. "-'F~he gasometer was now charged with earburetted hydrogen, and placed in a mercury bulb, with its mouth immersed in quicksilver. I t was subjected to different pressures, and it began to liquefy at about 40 atmo.~heres, and at lg00 atmospheres the whole was liquefied.

Mr. Perkins is now occupied with the construction o f a sultable apparatus for ascertaining the law of condensation of gaseous fluids, at high degrees of pressure. [Brewster~s Jouriial~

On the ~iethod of Striking the Medallions, termed by the French " E n Clichd.'--By TI-IOMAS GILL, ESq.

OuR readers must have frequently seen the~beautifhl impressi0ns, or medallions, from tile Revolutionary, Napoleon, and ather meda|s~ struck duri~Jg the late wars with France, and which Were uSua!l~ bronzed, mounted into the lids.ob~iluff-boxes,,:a'ad~dgf¢,nd.ed~ injury, by bein~ covered witl~ofivex glasses# ~ ::~:~ ~:: ~ : : : ;:~i :

We have lat~l~ been highly gratified, b y i)~6g:.permitted tO Wit- ness the fabricaUon of these medallions; and from the information we then receivad, and particulars derived from other sources of in- telligence, we trust to be able to furnish such an account thereof, as will enable others to imitate them.

It is a lkct, that, either frou~ a medal struck in any of the usual metals, from a s ~ steel die, or even from one of th~se medallions themselves, dies may be readily made, each of which will be capa- ble of striking a considerable number of such medallions, and each of these, in its turn, be capable of producing a multitude of Other dies, likewise fit to become the origin of as many successive medallions, and dies; so that, by this means, the original medal may be copied almost ad infinitum ! Each remove from the nriginal however; iosi ng~ of course, somethin~ of its sharpness, and accuracy of finish~ al- though much less th~n might be supposed, and far less than by the usual methods of copying medals, by moulding and casting them.

We cannot but be surprised that so valuable an art; should hi- therto, in this country, have remained in so few hands; as, ['ram the succeeding details, it will be found to be abundantly simple, and easy tO e x e c u t e .

Of the metal used in Jb~ning the Dies and the MedaUions.

This nmtal is composed of the ordinary t!/pe metal, w hich is an alloy~t~ lead, and regulus of antimony, to whicl~ l~s added more and more~le'~ i until' on trial, by repeatedly breakin~ a plate cast from the mixtu~i:~ii~ is tbund to bern] a little, before breal~ing. This is oue of the be~;~ri= terions to judge by, as, fi-om the variety of proportions of lead ~uii]~/~egu - us eu played by &ffcrent type-launders, no certain proportions cart

4. Ma. GH.r., on a I#rench Method Of Striking Medalli'onso

be antieipated~ in the composition of tile broken types, which are pm'o chased fir this use.

This compound metal is made, and melted, in a cast-iron pot, such as is used in cooking, and whicli is Suspended o~¢er ihe fire, by its bail, or handle. 'l'h-e alloy, when a sma'll quantity of it iS taken up in an iron ladle, and kept-in continual too{ion by'shaking the ladle round and round, whilst it is cooling, at length assumes apasty con- sistence, or a commencement of crystallization: this isthe proper mo- ment for employing it~ either to fo{m a die, or a medallion, by striking the original medal, or medallion, or a die upon it, in the manner to be hereaf{er described; when, from its pasty'coherence, it cannot slip away from the blow, and is yet sufficiently plastic to receive the impression of the medal or die.

The compound metal, at the above period, does not retain heat enough to singe, or even to discolour the paper upon which it is laid~ to receive the impression; and this again forn{s another valuable criterion to judge by, whether the alloy is rightly proportioned or not.

I t would hardly be thought that tlns alloy, or composltmn, should • . . - - . ~ - , •

be capable, both ot forming the dm or mould, and also of ymldmg nu- merous impressions frmn it, and yet such is the fact: a uiost remark- able discovery, and one, indeed, upon which the great merit of the art chiefly rests.

7:ype metal may consist of about live parts of lead, and one of re- gulu's of antimony. Tim lead bein_~ melted in a,1 iron vessel, the regu- lus must be stirred in it, continua~lly, and be kept immersed in the lead, until it is at length dissolved, or melted iia it: this, however~ is a work of time, and very much depends upon the due heat given to the lead, whicl~ ought to be a little, though not much, above its melting point, lest it oxidate. The surface of the lead ought also to be covered with rosin, pitch, or grease, to prevent such oxidation as much as possible. The goodness of the type metal depends very much upon the quality of the regulus which enters into its composition. This metal, contains more or less iron ~ c,r tin, (fl'om the clippino~s of tin ned iron plates being generally preferred, in this countr~'fol Y making the regulus fl'om the ores of antimony.) Copper, when used, parti- cularly; tits it for makblg a whiter newter, than the re,,'ulus made withirom ~,Ve have seen, recently, a very superior kind'of regulus, nearly fi-ee fi'om at~y admixture w~th either of those metals; so that the nature of the type metal, as we have before said, is infinitely va- rious.

These impressions are also taken, by the French, in what they term ~ Darcet's alloy," but which we know under the name of ,5*ir Isaac 5~ewton'sfusible metal, being a compound of three parts of tin, five of lead, and eight of bisumth, and capable of melting in boiling water. This metal, although more expensive~is harder than that above described, and is capable of giving exceedingly sharp impres- sions. A still better metal wouhl however~ be~ G. &,~ith's soldm'jbr tin, as it is not so liable to mTstallize in cooling, as the fusible metal;

" 8,ee an article by Mr. Gill, on alloys of caat-irmb with lead~ *bl, and regulus o fan t imow. , Vol. 1I, p, 374.

Mn. GmL, on a French .Methodof Strikinff MedallionS. 5

this is composed of one part each, of lead and tin, and two p a r t s ~ bismuth.

On the machines employed for Striking the Dies and Impresslbhs,.~ The well known button stamp may be used; but the onewe saw, had

only a single, square, iron rod, or stem~ guided above in two squar~f halv'ed hol~s, and having a ring handle to raise it by. This apparatus was mounted upon the top of a three-sided close box, like a corneL" cup~ board, set upon the floor, with a door opening in front~ the rod passe-d through a hole made in the top of the box, and had appended t o i ~ a brass, or gun-metal frame, having four screws or~ the under side of it~ passing through, made in as many ears formed la the frame¢ exactly Iike the ordinary die dish, employed to hold dies, &c. in the lathe~ in order to turn them. These screws crossed\at right angles, :th~eir points all tending to the centre of the frame, which was made quite fiat on its under side. A soft bell-metal, or gun-metal, cylindrical ring, was held, or suspended, between the four screws, and it also con- tained an inner gun-metal ring of the same depth as the former~ but its inside was made in the shape of two inverted cones, the:use of which will be hereafter described. The inner ring was:held fas~,:~by means of a single screw fixed in the outer rih~g,~bi~ding upon it: ~h'~ frame had also a groove made around the upper, or c~rlir~drical' part of it, into which a catch, or detent, was fitted, which was mounted upon an axisin the centre, and its other, or outer end, was shaped into an inclined plane, hanging over the door of the box, and so contrived, that, instantly, on shutting the door, the detent was raised, and let the fl'ame fall. The bottom of the box had a flat plate of cast-iron laid upoIt it, to support a tray of paper in the middle of it, andupon which the lmnp of heated alloy was placed, in order to receive the impressions, and the door and sides of the box were linedwith sheet lead all around their lower parts, to catch the exccss of metal which splashed around, from the force of the blow upon the heated metal.

Other machines of this kind have had the rapidity of the ideSeeat of the frame increased, by means of springs in the form of.~bb~i~.. acting uponit. '. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The door of the box being opened, the detent was-ena'a~ed in the groove made in the top of the fi'ame, which also passed~th~'ough the hole in the top of the box, and held it up, whilst the heated mass of metal was being laid upon the paper, but instantly released it, and

• " - - " o - - • - - suffered tt to fall, upon shutting the door of the box. We have now betbre us, the obverse of one of Buonaparte's me-

dais, in the state in which it was produced from the blow. It is one and a half inches in diameter on its face, but widens behind to ol~e inch and five-eighths, it being conical on its edge. It is one-eigh~li of an inch !n thickness, this being intended to be reduced, by tt/rrif~g it away at its back, in a lathe of a peculiar construction.

We have said that the innermost of the two gun-metal rings, hadits inside made in the shape of two inverted cones. The lovJefmost of these cones, gave the conical form to the edge, or rim, of,the medal-. lion, and was consequently one-eighth of an inch in depth. The

6 MR. GILt., on a French Method o f Striking Medallions.

uppermost, or reversed cone, was formed of the same angle, but wa~ seven-eighths of an inch deep, the thickness of the ring being one inch. The die from which this medallion had been struck~ was tbrmed by carefully filing the conical rim.of a similar medallion~ until it accu- rately fitted the lower part of the reversed Cone, the face of tile me- dallion being let into the cone, even with the line of meeting of the two cones. Some of the metallic medallion alloy, was then poured into the remaining space in the cone above the medallion, until it filled it up, exactly even with the flat surface of the ring. By this judicious contrivance,the medallion was effectually prevented from rising, ill striking the blow, by means of the fiat face of the alloy, thus poured in above it, coming into contact with the flat undermost face of fl.m

revented from falling, by the cone m carrying fl'ame; and it was p which it was held. In tiffs state, the ring, and the medallion in it, being fastened in the outer ring, by the screw in it, and a mass of the melted alloy laid upon a thick paper tray, supported upon the itat cast- iron plate below, as above described, the fl'ame, rings, and medal- lion, beine first raised and held up by the detent, the blow was struck npon the ~nelted alloy, and the excess of metal being scattered on all sides; in which it was aided by fbur shallow gaps, filed across the flat bottom of the ring, to permit the air and extra metal to escape the mort readilv;~ Ul.)on removing,, the irg. l..)ression fl'om, the die,. by means of one of the portmns of metal, winch filled one ot these lour grooves, together with the conical or widening form of the mouth of {he vinv', a female impression of the medallion was thus produced; whiciL on being, in its turn, accurately filed on its rim, so as to fit into tt~e uppermost cone of the ring, exactly, and, as was above described iu fixing tim medallion into it, and the space aboveit being also filled with melted metal, thus formed the die, from Which our medallion was struck, and was evidently capable of striking many such. We have to add, that, although the outer , ing ,,,as capable of receiving witMa it, other rings, of one uniform external diameter, that the inside cones of which were fitted to many ditthrent sized medallions, yet that various sizes of outer rings were also provided, in order to extend the capability of the apparatus to strike the larger medallions also.

Two diflbrent[ff Jitted up lathes, were employed in this lnamtfac- ture. The one, to turn the conical rims of the medallions to a cylin- drical form, and to prepare them to be afterwards reduced at the other, to a woper thickness and flatness. The medallion was held central in the first lathe, by its circular border being received upou the sharp circular edge of a concave gun-metal dish, or chuck, screwed upon the lathe mandrel; which permitted the raised impres- sion to be lodged in it, and it was pressed into contact with the dish or chock, by a central point, urged against its hack by a screw. In this situation the conical edge or rim of the medallion was readily tin'ned cylindrical, by a tool properly held and guided in the lathe. There was afterwards little ditficulty in holding these medallions, thus made cylindrical, Ul)On their edges, in prol)er dmcks, fitted uporl the. mandrel of the other lathe, and in al~plyin,,, a turnina'-tooI~o io thmr backs} to Ou't~ them llat~ attd ot a proper thtc~nes;;, ht cas%

M. VERBY, on Bronz ing Medallions, ?

however, of medals being to be formed of these medallions,.the~:two parts, forming the obverse and reverse, were first cemented'together at their backs, and then placed in a tMrd lathe, furnished ,wi(h two similar concave gun-metal dishes or chucks, the one placed :behind, and the other in front of the medallion, to support it;. and the ;one of them being screwed upon the lathe mandrel, and the other havin~; a hole in its centre, which was lodged and turned upon the eonietil back centre of the lathe: the double rims could thus be turned toge- ther, to a perfect cylinder.

Die Sinkers may avail themselves, with advantage, of this method of taking impressions from their soft dies~ during the progress of their execution; and indeed we have an impression from a dl"e of the late Mr. Johnnis, of Hafod, thus produced, by that excellent artist~ the late Mr. Mills.

Larget:.y..p es, orblocks, for p rintin g ,ma y also thus be m u l t i . , . .p lied, with. great facility and correctness, even more so, than by stereotyping them.

We subjoin the following article, on Bronzing these Medallions, observing, by the way, that it is sta{ed to be for bronzingtln. Th~ French applTmg the term L Etain indifferently both to tin and ew- ter; a practi~e which fi'equently leads to great in:converiieneein tffa~s- lating fi'om that language. [Technlcal Repository.

On Bronzing the Medallions Struck in Soft Type Metal, or Fusible 3lclal .~By M. V~it~y. J, un. ~

To perfectly succeed in bronzing these mddallions, we must em- ploy the two following solutions: tim first, which serves as a prepara- tory wash, to be used as hereafter described, is composed of one pal/t of sulphate of iron, one part of sulphate of copper, and twenty parts (by weight) of distilled water.

The second solution, which is the bronze, is less complicated; it is composed of four parts of verdigris, and sixteen parts (by~yveight) of white French vinegar.

The ~[anner of Em,ploying these Solutions.--When the medallions have been filcd and polished, on their edges, and strongly rubbed with a brush, wetted with a mixture of tripoli, or rotten-stone, and water, and well washetl anti dried, we pass the first solution slightly over both their faces, ~ith a hair pencil, and then wash and wipe tile medallions dry; this gives them a slightly blackish colour, and causes the verdigris to adhere more quickly to them. Theyare then rub, bed with another hair-pencil, wetted with the second solution, untfl they become of a deep copper colour; they are then left to dry for an hour, after which they are polished with a soft brush, and redlead, breathing upon them fl-equently, to slightly moisten them, and ;cause

" From 27eeue, il des travaux de la $oe. de Lille, 1825..