Assaying is the estimation of the amount of pure metal, and especially of the precious metals, in an ore or alloy. In the case of silver the assay is either by the dry or by the wet process. The dry process is called eupellation from the use of a small and very porous cup, called a cupel, which is usually made of well-burned and finely-ground bone-ash or of magnesia. The cupel, being thoroughly dried, is placed in a fire-clay oven about the size of a drain-tile, with a flat sole and arched roof, and with slits at the sides to admit air. This oven, called a muffle, is set in a furnace, and when it is at a red heat the assay, consisting of a small weighed portion of the alloy wrapped in sheet-lead, is laid upon the cupel. The heat causes the lead to volatilize or combine with the other metals, and to sink with them into the cupel, leaving a bright globule of pure metallic silver, which gives the amount of silver in the alloy operated on. In the wet process the alloy is dissolved in nitric acid, and to the solution are added measured quantities of a solution of common salt of known strength, which precipitates chloride of silver. The operation is concluded when no further precipitate is obtained on the addition of the salt solution, and the quantity of silver is calculated from the amount of salt solution used.
An alloy of gold is first cupelled with lead as above, with the addition of three parts of silver for every one of gold. After the cupellation is finished the alloy of gold and silver is beaten and rolled out into a thin plate, which is curled up by the fingers into a little spiral or cornet. This is put into a flask with nitric acid, which dissolves away the silver and leaves the cornet dark and brittle. After washing with water the cornet is boiled with stronger nitric acid to remove the last traces of silver, well washed, and then allowed to drop into a small crucible, in which it is heated, and then it is weighed. The assay of gold, therefore, consists of two parts: cupellation, by which inferior metals (except silver) are removed; and quartation, by which the added silver and any silver originally present are got rid of. The quantity of silver added has to be regulated to about three times that of the gold. If it be more the cornet breaks up, if it be less the gold protects small quantities of the silver from the action of the acid. Where, as in some gold manufactured articles, these methods of assay cannot be applied, a streak is drawn With the article upon a touchstone consisting of coarse-grained Lydian quartz saturated with bituminous matter, or of black basalt. The practised assayer will detect approximately the richness of the gold from the colour of the streak, which may be further subjected to an acid test. The Goldsmith's Company of London is the statutory assay-master of all England. Research Assaying
A bell is a hollow, somewhat cup-shaped, sounding instrument of metal. The metal from which bells are usually made (by founding) is an alloy, called bell-metal, commonly composed of eighty parts of copper and twenty of tin. The proportion of tin varies, however, from one-third to one-fifth of the weight of the copper, according to the sound required, the size of the bell, and the impulse to be given. The clearness and richness of the tone depend upon the metal used, the perfection of its casting, and also upon its shape; it having been shown by a number of experiments that the well-known shape with a thick lip is the best adapted to give a perfect sound. The depth of the tone of a bell increases in proportion to its size.
A bell is divided into the body or barrel, the ear or cannon, and the clapper or tongue. The lip or sound-bow is that part where the bell is struck by the clapper. It is uncertain whether the jangling instruments used by the Egyptians and Israelites can be correctly described as bells; but it is certain that bells of a considerable size were in early use in China and Japan, and that the Greeks and Romans used them for various purposes. They are said to have been first introduced into Christian churches about 400 AD by Paulinus, bishop of Nola, in Campania (whence campana and nola as old names of bells); although their adoption on a wide scale does not become apparent until after the year 550, when they were introduced into France.
Benedict Biscop, abbot of Wearmouth, seems to have imported bells from Italy to England in 680, but their use in Ireland and Scotland is probably of earlier date. The oldest of those existing in Great Britain and Ireland, such as the 'bell of St. Patrick's will' and St Ninian's bell, are quadrangular and made of thin iron plates hammered and riveted together.
Until the thirteenth century bells were of comparatively small size, but after the casting of the Jacqueline of Paris (6.5 tons) in 1400 their weight rapidly increased. Among the more famous bells are the bell of Cologne, 11. tons, 1448; of Dantzic, 6 tons, 1453; of Halberstadt, 7.5, 1457; of Rouen, 16, 1501; of Breslau, 11, 1507; of Lucerne, 71, 1636; of Oxford,7.5 1680; of Paris, 12.8, 1680; of Bruges, 10.5, 1680; of Vienna, 17.75, 1711; of Moscow (the monarch of all bells), 193, 1736; three other bells at Moscow ranging from 16 to 31 tons, and a fourth of 80 tons cast in 1819; the bell of Lincoln (Great Tom), 5.5, 1834; of YorkMinster (Great Peter), 10.75, 1845; of Montreal, 134, 1847; of Westminster (Big Ben), 15.5, 1856, (St Stephen), 13.5, 1858; the Great Bell of St. Paul's, 17.5, 1882. Others are the bells of Ghent (5 tons), Gorlitz (10.75 tons), St Peter's, Rome (8 tons), Antwerp (7.25 tons), Olmutz (18 tons), Sacred Heart, Paris (27 tons), Novgorod (31 tons), Pekin (53.5 tons).
Besides their use in churches bells are employed for various purposes, formerly the most common use being to summon attendants or domestics in private houses, hotels, etc. Bells for this purpose were of small size and may be held in the hand and rung, but most commonly were rung by means of wires stretched from the various apartments to the place where the bells were hung. Bells rung by electricity became common in hotels and other establishments around 1905.
Carat is the unit of measurement of gold purity - the proportion of gold to other metals in the alloy, expressed in 24ths. Coinage contains 22 parts of gold and is therefore described as 22 carat, pure gold is 24 carat. The carat is also a unit of weight, equal to 3.17 troy grains, used in the weighing of precious stones. Research Carat
Eureka (from the Greek heureka, I have found it), is the exclamation supposedly made by Archimedes when, after long study, he discovered a method of detecting the amount of alloy in King Hiero's crown. Hence the word is used as an expression of triumph at a discovery or supposed discovery. Research Eureka
Archimedes was a great ancient Greek mathematician and physicist. He was born about 287 BC at Syracuse, in Sicily. He devoted himself entirely to science, and enriched mathematics with discoveries of the highest importance, upon which the moderns have founded their admeasurements of curvilinear surfaces and solids. Archimedes is the only one among the ancients who has left us anything satisfactory on the theory of mechanics and on hydrostatics. He first taught the hydrostatic principle to which his name is attached, that a body immersed in a fluid loses as much in weight as the weight of an equal volume of the fluid, and determined by means of it that an artist had fraudulently added too much alloy to a crown which King Hiero had ordered to be made of pure gold. He discovered the solution of this problem while bathing; and it is said to have caused him so much joy that he hastened home from the bath undressed, and crying out, Eureka! Eureka ! I have found it! I have found it! Practical mechanics also received a great deal of attention from Archimedes, who boasted that if he had a fulcrum or standpoint he could move the world. He is the inventor of the compoundpulley, probably of the endless screw, the archimedean screw, etc. During the siege of Syracuse by the Romans he is said to have constructed many wonderful machines with which he repelled their attacks, and he is stated to have set on fire their fleet by burning-glasses! At the moment when the Romans gained possession of the city by assault in 212 BC tradition relates that Archimedes was slain while sitting in the market-place contemplating some mathematical figures which he had drawn in the sand. Research Archimedes
The 3rd Pattern Commando Knife (Fairbairn-Sykes) was a double edged fighting knife designed by Fairbairn and Sykes as a grip-heavy fighting knife that could be held in the fencing position. It was specified by the British MOD in 1943, and issued to Service Men. It had a tapered diagonal-section 7 inch, double edged carbon-steel dagger blade with a two inch oval guard, a ribbed zinc-alloy handle and a brassnut. The blade was finished in black. Research 3rd Pattern Commando Knife
The Colt Mustang is a series of American small service pistols of the Colt MKIV Series 80 range chambered for the .380 Auto (9 mm Short) cartridge which they take from a 6-round magazine. The Colt Mustang series have a 70 mm long barrel, fixed sights and come in two basic variations, the standard and the lightweight 'Pocketlite' variation which has an aluminiumalloy frame. Research Colt Mustang
The FN 140 DA is a Belgian double-action, blowback operated self-loading pistol manufactured by FN first during the 1970's and intended for general purpose defensive use by military and police forces. The FN 140 DA features a light-weight alloy frame with a steel slide. It is chambered for the 9 mm Short or 7.65 mm cartridge and takes a 13- or 12-round box magazine respectively. The FN 140 DA has a muzzle velocity of 27-290 m/s with the 9 mm Short ammunition and 290-300 m/s when firing the 7.65 mm calibreammunition. Research FN 140 DA
HE MOM is a multirole ammunition in which preformed cubes of tungstenalloy are held in position around the projectile body by steel liners and able to pierce up to 6mm steel. The new proximity fuse makes the projectile very effective also in the anti-ship role. When the proximity function is paralysed, the fuse has a delayed PD action which ensures that the projectile penetrates the hull before bursting. Research HE-MOM
The Probert Encyclopaedia was designed, edited and programed by
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Abbreviations
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