GOLD.— Coining.

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This practice has only been adopted in the case ofsilver since the latter end of 1873; so that with thismetal and gold the process of pickling or blanching,formerly considered important, is now almost entirelydispensed with. This included three distinct opera-tions :—

(1) Heating the blanks and exposing afterwardsto air, thus forming a film of oxide of copper ontheir surface.

(2) Removing this film by solution in dilute acid.

(3) Drying the blanks.

In the case of gold, as already mentioned, thisoxidation of copper took place while the tubes werecooling in the air, while silver blanks were exposedfrom the commencement, being introduced into thefurnace in open iron trays. The blanks, while in thecolander, were cooled in water and dipped into a bathof dilute sulphuric acid (specific gravity, 1-021) wherethey remained for a few minutes, the oxide of copperbeing thus dissolved off and leaving a surface of puregold or silver. They were then washed and dried insawdust as above described. Blanching undoubt-edly has the advantage of giving to the coins a betterappearance when first issued from the Mint, but thisthin superficial layer wears off much quicker than anequal thickness of the standard alloy would do: hencegold coins will continue a less time in circulation,being reduced below their least current weight. Thequestion is, however, of but small importance tothe public.

The annealing of copper blanks was formerly avery slow process, as the cast-iron tubes in whichthey were placed in the furnace were afterwards leftto cool in the air by radiation, the blanks being thenplaced in dilute sulphuric acid for several hours.The method now adopted is a modification of theabove, the tubes being, immediately on their with-drawal from the furnace, immersed in cold waterand rapidly cooled; the blanching is performed asheretofore.

Coining .—The blanks having been thus prepared,nothing remains, as far as forming a completed coinis concerned, but to introduce them one by one intothe coining press, whereby, at a single blow, not onlythe obverse and reverse impressions are given, butthe crenated or “ milled ” edge is formed on thosecoins which require it. The presses employed in theBritish Mint are extremely antiquated, having beeninvented by Boulton, and made by the well-knownfirm of Boulton & Watt, and are of the formgenerally known as screw-presses. The blanks,having been arranged in a vertical hopper, are placedone by one in the press upon the lower die, which isfixed, by means of an automatic hand. Immediatelyupon the withdrawal of this hand a collar, slightlylarger than the blank, rises round it in such a mannerthat, when the upper die is brought down with con-siderable force upon it, the metal is pressed againstthe inner rim of the collar, and as this is crenated,the edge of the now finished coin, on its removal, is“milled” in a corresponding manner. It is unne-cessary further to describe this unhandy, noisymachine, which must ere long give place to some of the

lever presses now almost universally employed on theContinent. The lever press is compact, and does itswork in comparative silence. It is already in usein the majority of the continental mints, and atCopenhagen , where formerly presses similar to thosein the Royal Mint were in use, the lever press hasalso been introduced. There are two forms in use,one invented by Tiionnelier and the other byUhlhorn. The power is communicated to a crankshaft, from which it is transmitted by a connectingrod to a lever and toggle joints, which actuate thearm carrying the upper die, by which means thepressure is given slowly and without a shock. Thepress, in addition to the advantages already men-tioned, has the merit of being compact, simple inconstruction, and easily accessible for repair. It canbe driven by a strap from a running shaft, and doesnot require a special foundation for its reception.

Weighing Individual Coins .—In nearly all the conti-nental mints the blanks, immediately on being cutfrom the fillet, are weighed in order at once to rejectthose which would, if passed to the subsequentoperations, produce illegal coins. In some mintsthose blanks which are too heavy are reduced inweight, the weighings necessary for this adjustmentbeing performed by hand. In England and Spain ,however, the individual weighing is only performedon each finished coin, and thus all the blanks areconverted into coin; and although this entails theproduction of a certain number of finished coinswhich are ultimately rejected, it unquestionablyaffords a better guarantee for the maintenance ofthe legal weight of the coins. In this country theweighing is performed entirely by automatic mach-inery, and the apparatus employed for the purpose isthe most remarkable and, except that employed inthe Assay Offices, the most delicate in the Mint.The original form of this instrument was the inventionof Cotton , but in those now in use several improve-ments have been adopted. No less than nineteen ofthese balances are now employed, each being capableof weighing twenty-two coins per minute to thehundredth part of a grain. The machine consists ofa beam, on to one end of which is affixed a plate ortable, and upon this the coin to be weighed is placed.The other end of the beam is provided with a scalepan containing a counterpoise weight correspondingto the coin in question, and a small stirrup or fork isaffixed to the under surface of the pan. In certainpositions of the beam this stirrup lifts up a small wirewhich represents the remedy weight of the coin. Theaction of the machine is as follows:—

A coin is placed upon the pan; if too heavy thecounterpoise weight is raised together with theremedy wire; if too light, both the weight andremedy wire remain undisturbed; but if the coin iswithin the working remedy, the counterpoise weightis alone raised. The coin is then sent down a shoot,the position of the lower extremity of which overone of three slits is determined by the mechanismof the apparatus, and varies according as one or theother of the above conditions prevails. Those coinswhich are by this process ascertained to be of the