1845.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



187 



(luri- Rolcl, the remaining twclflli in it being what goes under the name of 

 " alloy ;" it may, of course, consist of any mcta', necessarily of an inferior 

 value to f^olcl, wliich docs not inalerially affect either the colour, malleability, 

 or durability, of the noble metal. In fact, there are only two metals practi- 

 cally employed for the purpose, namely, copinr and silver. Thus the twelfth 

 part, which is called alloy, may Ix' silver, or a mixture of silver and copper. 

 This was generally the case, till of late, means of extracting silver with profit 

 have been devised ; so that now, when the ingot of gold comes to the Mint 

 or Hank containing silver, as well as copiicr, ihat silver is reported on, and 

 as far as the ingot goes it constitutes increase of value, because it may be 

 sent to the refiners, and the refiners may extract that silver and replace it by 

 copper, and then return it to the Mini, and still pass as standard ; because 

 everything ia considered except pua' gold as alloy. AVhellur the twelflh 

 l>art consists of silver or copper is of no conse(|uence to us, but matters con- 

 siderably to the owner of the bullion. These points are very curious and 

 would interest if the lecturer could, upon one evening, have brought the whole 

 subject in detail, showing how small a quantity of silver will pay for the 

 oiwratlon of extraction. All this depends entirely on the great improvement 

 which has taken place of late years in the chemical .arts, especially in the 

 manufactory of great engine of chemistry, sulphuric acid, or oil of vitriol. 

 It may be added, also, that we owe much to Dr. tt'ollaston's mode of work- 

 ing platina so as to enable us to employ platina ; and it is cheapness of oil 

 of vitriol on the one band, and the possibility of using platina on the oilier, 

 that has enabled the refiners to bring this process to such perfection, so as, in 

 fact, to take the silver out of the gold with a profit. 



lliere is an important circumstance cennectcd with the alloy, nsmely, the 

 endur.ance of friction In circulation. It appears from the experiments of 

 Messrs. Halchett and Cavendish, that an alloy of eijual parts of silver and 

 copper was most effective in that respect; and, accordmgly, when we have 

 alloy in an ingot of metal containing eleven parts of pure gold, the remaining 

 twclflli being half copper .ind half silver, that is the article, perhaps on the 

 whole, best adapted for coinage. There is one pnint, however, of great im- 

 portance in all these steps, which is this, that the copper which is used for 

 alloy should be absolutely pure ; for if it contain a minute quantity of cer- 

 tain other metal it does infinite mischief to the gold, and, above all, renders 

 the ingots brittle and intractable, so that tliey cannot be rolled or worked in 

 the succeeding operations. There are tw o colours of sovereigns at pr.sent in 

 circulation ; one kind, the pale sovereigns, are fast disappearing — those arc 

 the sovereigns which contain silver ; the dark looking being such as are al- 

 loyed exclusively with copper. Standard gold, that is, gold to which one- 

 twelfth alloy has been added, coins better, and sustains wear and tear l)etter, 

 and it is more fusible than pure gold ; pure gold being so soft as to bend, and 

 so tough as to clog the dies, besides the great difficulty, and, indeed, impos- 

 sibility, that we had of procuring and preparing it for the purposes of 

 coinage. 



It is curious to observe the extreme difficulty in getting a perfectly uniform 

 bar. Kven shadows of difference that would not be noticed are important. 

 There is a very curious document in existence, published on the operations of 

 a part of the Mint, showing the great difficulty of making what are called 

 trial plates. That is, in making the standard plates, which are to be uniform 

 throughout, and which are to be deposited in the exchequer and elsewhere, 

 for reference upon emergency and particular occasion, to determine the purity 

 of the coinage. 



In the case of the importation of silver the same general rides arc adopted 

 as in regard to gold ; but, n ilh us, the standard silver differs from that of 

 the gold, the former being an alloy of which there are llr^ silver and ii 

 copper. It will be observed that our standard is high, and above that of 

 France; both in regard to gold and silver, the standard is nine of noble 

 metal to one of alloy or -^. Now, it is found generally, in regard to alloy 

 of silver and copper, that the specific gravity of the standard alloy is 10-fi;, 

 and this is a tittle below the Mint ; so that silver and copper, when made into 

 an alloy, undergo a slight dilatation, or diminution of specific gravity. The 

 present account will be limited to geld coinage, which involves in its general 

 outline the course adopted equally i.i silver and copper coinage ; but gold 

 coinage requires the extremest accuracy and nicety in all its details. It is 

 our standard value, and no charge for labour or expense of coinage, and a 

 furliari, no profit, shall then l)e taken on it, so that an individual bringing 

 gold to the Mint receives in return the full value in coin, which, of course, is 

 more valuable than the bullion, in so far as it bears a stamp which is a secu- 

 rity for its circulation over the whole civiliz.ed world. 



The fineness, value, or composition of the ingots having been determined, 

 and the whole having been adjusted to standard, the ingots are handed over 

 to the melter, with proi>cr directions for melting and casting them into stand- 

 ard bars. The melter receives a quantity of ingots with a paper telling him 

 how he shall pot those ingots, that he shall take such and such numbers, and 

 such and such. The gold is melted in what are called black-lead pots, each 

 of which ii placed in a separate furnace, and holds about one cwt. of gold. 

 They cast in iron pots the bars of the shape shown, if intended for sovereigns, 

 but if for Ualf-iovcreign>, tb« bars Br« smaller. The sihet is melted in a 



inucli larger pot, in fact in a pot which Iiolds from 400 to 500 lb. The gold 

 melting pots are known under the name of black-lend pots ; they are ex- 

 tremely refract"ry and bear a high degree o( heat without a cliancc of 

 cracking, if carefully used, and will .admit of being lifted out of the fire with- 

 out risk, which is important, because, it is obvious, tlmt if by any accident u 

 pot of metal gets broken and falls, a great deal would be destroyed and lost 

 at the cost of the melter. In order to enable these crucibles to hold a num- 

 Ijcr of ingots, before they arc run down in this w ay, they put them into another 

 crucible, technically called a muflin ; then the whole is covered up and healed 

 in a common wind fuinace. until the w hole is melted ; they are then carefully 

 stirred and lifted out of the furnace by a particular but very convenient kind 

 of leverage, and then are poured carefully into the moulds; there is a great 

 deal of care requisite in that operation in order to prevent the gold fining or 

 refining, as it is called ; that is, if not carefully done, part of the alloy (the 

 copper) will separate from it, and conseijuently, it will turn out too fine ; the 

 Melter, therefore, has, in the first place, to take cave that the mixture is uni- 

 form in the pot ; in the next p'ace, to take care that part of the alloy is not 

 destroyed, because the pure gold is not altered by beat, but thecop|ier isoxy- 

 dized and goes away in dross. The silver melting-pots are made from cast- 

 iron, and contain from four to five cwt. of metal. Formerly the silver was 

 melted in small pots like the gold. This great improvement in melting we 

 owe to the present Deputy Master of the Mint, Mr. MoiTison, who, when he 

 came into the office, completely reformed the process of melting and pouring 

 the silver. Now, these are placed in proper wind furnaces, of course ; they 

 are then poured by machinery into moulds ; ami then again, great care is 

 required to stir the metal before it is poured, and again, to prevent its fining 

 or burning out the copper. In the present arrangement of the Mint, about 

 10,000 lb. weight of silver is very easily melted every day ; in fact, at the 

 present moment, a larger cjuantity is melted daily. Of course, in carrying a 

 large quantity of these heavy metal bars about there is a good deal of diffi- 

 culty in the mere carriage, this is efleclod at the Mint usually in little trucks 

 which run on iron wheels on railroads for the purpose, there being a commu- 

 nicition between the w hole of the offices by means of the railroad. In that 

 way they travel from one to the other. 



The Company of Moneycrs receive and are responsible for (he bars ; under 

 their superintendence and direction the money is maoufnctured, and it is ulli- 

 tnately delivered by them weight for weight through the money-office to the 

 importers. The moneyers are an extremely ancient company ; a company 

 that may be tr.iced back to a very remote period. M'hen the bars are passwl 

 to the moneyers they are first received into the rolling room. The first ope- 

 ration they undergo is usually called breaking them down ; the bar is squeezed 

 between rollers, which extend and elongate it into a thick fillet about 8 feet 

 long ]_^ inch broad an<l } of an inch thick ; this is cut in pieces of almost IS) 

 inches in length, and passed between rollers till each is 3 inches wide and ^ 

 of an inch thick. In this process of rolling the metal becomes hard, and it is 

 necessary from time to time to anneal it. Now this is a very nice process, 

 and consists in making a quantity of metal red hot and allowing it to cool 

 slowly. But then there is the difficulty, that if it be done in the air part of 

 the copjicr becomes oxydized or lost; therefore the pieces are carefully put 

 into a copper cylinder and heated out of contact with the air. They arc 

 heated to a red heat, and then the metal Ijecomes softened. Tlie last rolling 

 operation brings the ribbon to nearly its required thickness. A piece is now 

 cut out and if found to be of proper weight— that is, a little above what the 

 sovereign is ultimately to be. — the ribbon or fillet is then handed over to a 

 further process of manufacture. It is rolled down in the first instance by 

 the simple operation of rolling to a considerable degree of nicety. The rol- 

 ling of the mint is pirfectiy distinct from the rolling of iron, copper, or other 

 metals is commonly carried on. The utmost nicety is required to proportion 

 the edges and parts of the ribbon to the particular thickucss, which is deter- 

 mined l;y very nice guages ; above all to take care that there sh;dl be no in- 

 equality in the pressure, so that one side of the bar should become thinner 

 than the other. It is necessary, further, to take caie ihat the ribbon is per- 

 fectly true, not curved or curled in anyway, and that the edges especially arc 

 correctly squeezed out. All these are matters of extreme difficulty in prac- 

 tice, but most highly essential, in order to avoid a great deal of trouble « hieli 

 must result if points of this kind be not attendwl to in the earlier process of 

 manufacture, i'lie final .adjustment of the thickness is done by a machine 

 invented by the late .Sir John Barton, .and consists of a jicculiar process of 

 drawing. In this machine a most exquisite and surprising uniformity is given 

 to the thickness of the metal. 



When the sovereign is puncheil out on one side of the bars and out of thu 

 other it is weighed in a very delicate balance, and ought to be perfectly cor- 

 rect ; if it be not perfectly correct then a little more finish is given to the bar, 

 or it passes, if necessary, through a pair of very fine rollers again. That the 

 whole set of sovereigns cut out of the bar shall all be perfect as to weight Is 

 a matter of great nicety, but of great importance, and involving a number of 

 practical difficulties, which, however, have been wonderfully got over by 

 perseverance and the help of this machine. The ribbon being now completed 

 it is placed in the blank cutting-machine. This is a raachioe with twelve 



