MINT 



330 



minute portions of antimony in tho gold the bars are never of uniform thickness; 

 hence bars of every denomination are passed through the rollers on their edge, so as 



1524 



1525 



to reduce them to one uniform thickness, otherwise the fillets resulting would be 

 ragged, and of unequal widths, which defect would cause them to produce. blanks out 

 of remedy as to weight. 



When the metal is poured into the moulds, it almost immediately solidifies, and 

 while solidification is going on contracts in volume, leaving a kind of cup of metal, 

 or hollow part, on the top of the bar. In the act of rolling, the bar maintains an 

 equable width until this hollow part is reached, when it suddenly expands, and at 

 this point the workman shears off the defective part of the bar, because it would 

 ultimately cause dumb works. This operation is now performed in the melting- 

 house, before the bar is rolled, thus saving labour and loss of metal. 



The shears may be regarded as large sdssors, driven by a drum on the same shaft 

 that carries the driving-wheel for D. The drum is excentric, so that at each revolu- 

 tion the shears are caused to open and shut. 



The sheared bars for half-sovereigns are placed in copper tubes, the tops of which 

 are luted on with clay. It is imperative that the copper tubes should be made without 

 solder, because this fuses at a temperature below that which is required to anneal the 

 gold ; if present it would run down upon the 

 hot gold, and cause it to fuse and alloy with 

 the solder, thus spoiling the work and entailing 

 expense upon the coiner. The tubes which 

 were used in the Royal Mint were made by 

 Messrs. Benhams and Proud, of Chandos 

 Street, Strand, who, after considerable pains, 

 arrived at a method of making the tubes in 

 such a manner as to entirely satisfy the re- 

 quirements of the Mint. The tubes, A, are 

 placed on an iron carriage, B, which is then 

 run into tho furnace, as shown in Jig. 1525. 

 The door of the furnace, c, is closed by raising 

 the counterpoise; the heat of the furnace is 

 regulated by a damper. After remaining in 

 this furnace for twenty minutes, the carriage 

 is withdrawn, and the tubes, taken with tongs, 

 are plunged into cold water, to cool the gold 

 as rapidly as possible. The rapid cooling of 

 gold and silver gives to each metal a peculiar 

 character, which is of value in tho after pro- 

 cesses, and prevents the access of the atmo- 

 sphere, which, in prolonged cooling, would cause 

 the oxidation and consequent removal of so 

 much copper that tho alloyed metal would 



become too rich in gold for circulation as coin. After annealing, the bars, which 

 are now called fillets, go again to the breaking-down mill, through which they are 



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