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of reflecting telescopes, on account of the fine polish it is susceptible of, and its not being subject to tarnish. The alloys of gold with molybdcna are not known. It could not be mixed with tungsten on account of the infnsibility of this last substance. Mr. Hatchett gives the, following order of different metals, arranged as they diminish the ductility of gold; bismuth, lead, antimony, arsenic, zinc, cohalt, manganese, nickel, tin, iron, platina, copper, silver. The first three were nearly equal in effect; and the platina was not quite pure.
For the purposes of coin, Mr. llitchett considers an alloy of equal parts of silver and copper as to be preferred, and copper alone as preferable to silver alone.
Gold is found mostly in the metallic state, though generally alloyed with silver, copper, iron, or all three. It is found either in separate lumps, or visible grains, among the sands of rivers, in many parts of Europe and elsewhere. The quantity is, for the most part, insufficient to pay the cost of separating.it; but it is thought to be more universally diffused in sands and earths than any other metal, except iron. The greatest quantity of gold is imported into Europe from South America. Some is brought from the East Indian islands and China, and some from the coast of Africa. The principal gold mines in Europe are those of Hungary. Some sands afford gold by simple washing; the heavy metallic particles subsiding soonest: but when it is bedded in earths, or stones, these substances are pounded, and boiled with one-tenth of their weight of mercury together with water. The mercury, after a certain time, absorbs the gold, and may be separated by pressure through leathern bags, and subsequent distillation. Or, otherwise, if the sand be heated red hot, and quenched in water several times, for the purpose of cracking and dividing it, and the whole be then melted into glass, with twice its weight of the oxide of lead called litharge, and charcoal powder be then added, the lead will be revived in the metallic state, and will carry the gold along with it. By exposure to a proper degree of heat, with access of air, the lead may again be converted into litharge, and the gold will be left pure. This last operation is, in fact, a method of assaying sands which contain gold, rather than of obtaining it from them in the large way.
Gold is also found in certain martial pyrites in Sweden and elsewhere; from
which it may be extracted by torrefaction. or burning of the sulphur, and subsequent digestion in aquaregia.
To obtain gold in a state of purity, or to ascertain the quantity of alloy it may contain, it is exposed to a strong heat, together with lead, in a porous crucible. This operation is called cnpellation.
After gold has passed the cupel, it may still contain either of the other perfect metals, platina or silver. The former is seldom suspected; the latter is separated by the operations called quartation and parting. For all these operations see Assaying.
The quantity of alloy is never considered as part of the value of metals which contain either gold or silver. In estimating or expressing the fineness of gold, the whole mass spoken of is supposed to weigh 24 carats of 12 grains each, either real It merely proportional, like the assayer's weights; and the pure gold is called fine. Thus, if gold be said to be 23 carats fine, it is to be understood that, in a mass weighing 24 carats, the quantity of pure gold amounts to 23 carats.
In snch st ill works as cannot be assayed by scraping off a part, and cupelling it, the assayers endeavour to ascertain its quality or fineness by the touch. This is a method of comparing the colour and other properties of a minute portion of the metal, with those of certain small bars whose composition is known. These bars are called touchneedles; and they are rubbed upon the black basaltes, which, for that reason, is called the touch-stone. Black flint, or pottery, will serve the same purpose. Sets of golden needles may consist of pure gold; pure gold twenty-three and a half carats with half a carat silver; twenty-three carats gold with one carat silver; twenty-two and a half carats gold with one and a half carat silver, and so forth, till the silver amounts to four carats, after which the additions may proceed by whole carats. Other needles may be made in the same, manner, with copper instead of silver; and other sets may have the addition, consisting either of equal parts silver and copper, or such proportions as the occasions of business require.
In foreign countries where trinkets and small works are required to be submitted to the assay of the touch, a variety of needles are necessary; but they are not much used in England. They afford, however, a degree of information which is more considerable than might at first be expected. The attentive assayer not only compares the colour of the stroke made upon the touchstone by the metal under examination with that produced by his needle, but will likewise attend to the sensation of roughness, dryness, smoothness, or greasiness, which the texture of the rubbed metal excites when abraded by the stone. When two strokes, perfectly alike in colour, are made upon the stone, he may then wet them with aqua-fortis, which will affect them very differently if they be not similar compositions; or the stone itself may be made red hot by the fire, or by the blowpipe, if thin black pottery be used, in which case the phenomena of oxydation will differ according to the nature and quantity of the alloy.
Gold ores may be assayed in the moist way by pounding them very fine, weighing a determinate portion, and attempting their solution in nitric acid, which will dissolve the matrix if it consist of calcareous earth; or if it be sulphate of lime the powder may be digested in aqua-regia as long as any metallic substance is taken up ; after which the gold may be precipitated by an addition of sulphate of iron, which will cause it to fall down iu the metallic state.
The principal use of gold is as the medium of exchange in coin, for which it has been chosen to occupy the first place, on account of its scarcity, its great weight, and its not being subject to tarnish. The gold coins of Great Britain contain eleven parts of gold and one of copper. See Com.
Gold is likewise used in gilding. See Gilding.
The other uses of gold, in laces, See. are sufficiently known.
Gold heating. See Gold.
Gold wire, a cylindrical ingot of silver, superficial ly gilt, or covered with gold at the tire, and afterwards drawn successively through a great number of little round holes of a wire-drawing iron, each less than the other, till it be sometimes no bigger than a hair of the head. It may be observed, that before the wire be reduced to this excessive fineness, it is drawn through above an hundred and forty different holes, and that each time they draw it, it is nibbed afresh over with new wax, both to facilitate its passage, and to prevent the silver's appearing through it.
Gold wire fiafted, is the former wire flatted between two rollers of polished steel, to fit it to be spun on a stick, or to
be used flat, as it is without spinning, in certain stuffs, laces, embroideries, fcc.
Gold thfead, or spun gold, is a flatted gold, wrapped or laid over a thread of silk, by twisting it with a wheel and iron bobbins.
Manner of forming gold wire and gold thread, both round and flat. First, an ingot of silver, of 24 pounds, is forged into a cylinder of about an inch in diameter: then it is drawn through eight or ten holes of a large, coarse, wire-drawing iron, both to finish the roundness, and to reduce it to about three-fourths of its former diameter. This done they file it very carefully all over to take off any filth remaining on the forge; then they cut it in the middle; and thus make two equal ingots thereof, each about 26 inches long, which they draw through several new holes, to take off any inequalities the file may have left, and to render it as smooth and equable as possible.
The ingot thus far prepared, they heat it in a charcoal fire; then taking some gold leaves, each about four inches square, and weighing twelve grains, they join four, eight, twelve, or sixteen of these, as the wire is intended to be more or less gilt, and when they are so joined as only to form a single leaf, they rub the ingots reeking hot with a burnisher. These leaves being thus prepared, they apply over the whole surface of the ingot, to the number of six, over each other, burnishing or rubbing them well down. When gilt, the ingots are laid anew in a coal fire; and when raised to a certain degree of heat, they go over them a second time, both to solder the gold more perfectly and to finish the polishing. The gilding finished, it remains to draw the ingot into wire.
In order to this, they pass it through 20 boles of a moderate drawing-iron, by which it is brought to the thickness of the tag of a lace : from this time the ingot loses its name, and commences gold wire. Twenty holes more of a lesser iron leaves it small enough for the least iron; the finest holes of which last scarcely exceeding the hair of the head, finish the work.
To dispose the wire to be spun on silk, they pass it between two rollers of a little mill: these rollers are of nicely polished steel, and about three inches in diameter. They are set very close to each other, and turned by means of a handle fastened to one of them, which gives motion to the other. The gold wire in passing between the two, is rendered quite Hal, but without losing any thing of it* gilding, and is rendered so exceedingly thin and flexible, that it is easily spun on silk thread, by means of a hand wheel, and so wound on a spool or bobin.
GOLDFINCH. See Fringilla.
Gold size. See Size.
GOLDSMITH, or, as some choose to express it, silver-smith, an artist who makes vessels, utensils, and ornaments in ggfcl and silver.
The goldsmith's work is either performed in t he mould, or beat out with the hammer, or other engine. All works that have raised figures are cast in a mould, and afterwards polished and finished: plates, or dishes, of silver or gold are beat out from thin flat plates; and tankards, and other vessels of that kind, are formed of plates soldered together, and their mouldings are beat, not cast. The business of the goldsmiths' formerly required much more labour than it does at present; for they were obliged to hammer the metal from the ingot to the thinness they wanted: but there are now invented flatting-mills, which reduce metals to the thinness that is required, at a very small expence. The goldsmith is to make his own moulds, and for that reason ought to be a good designer, and have a taste in sculpture: he also ought to know enough of metallurgy, to be able to assay mixed metals, and to mix the alloy. The goldsmiths in London employ several hands under them for the various articles of their trade: such are the jeweller, the snuff-box and toy-maker, the silver turner, the gilder, the burnisher, the chaser, the refiner, and the goldbeater.
Gold, mosaic, that applied in panncls, on proper ground, distributed into squares, lozenges, and other compartments, part whereof is shadowed to heighten or raise the rest.
Gold, shell, that used by the illuminers to write gold letters. It is made with the parings of leaf-gold, and even of the leaves themselves, reduced into an impalpable powder, by grinding on a marble with honey. After leaving it to infuse some time in aquafortis, they put it in shells, where it sticks. To use it they dilute it with gum-water, or soap-water. , ^
Gold, pure, that purged by fire of all its impurities, and all alloy. The moderns frequently call it gold of '.-1 carats, but in reality there is no such thing as gold so very pure, and there is always wanting at least a quarter of a carat. Gold of fi carats
has one part of silver and another of copper; that of 23 carats has half a part, i. t. half a twenty-fourth of each. See Carat.
GOLDEN number, in chronology, a number shewing what year of the moon's cycle any given year is. See Chronology.
The rule for finding the golden number . is this; add one to the given year, and divide by 19, the quotient is the number of cycles which have revolved since the commencement of the Christian aera, and the remainder will be the golden number for the given year: the golden number for
1809 =18°9 "r*1 = 95 for the number of
cycles, and 5 the remainder will be the golden number: when there is no remainder the golden number is 19.
Golden rod. See Solidago.
Golden rule, in arithmetic, is also called the rule of three, and the rule of proportion. See Proportion, and Rule Of Three.
GOMPHIA, in botany, a genus of the Decandria Monogynia class and order. Essential character: calyx five-leaved; corolla five-petailed; berries two, on a large receptacle; seed solitary. There are three species.
GOMPHRENA, in botany, globe -maranth, a genus of the Pentandria Digynia class and order. Natural order of Amaranthi, Jussieu. Essential character: calyx coloured, outer three leaved; leaflets two, converging, keeled; petals rude, villose; nectary cylindric, five-toothed; style cloven half way; capsule one-seeded. There are pine species.
GONATOCARPUS, in botany, a genus the Tetrandria Monogynia class and order. Essential character: corolla four cleft, drupe eight-cornered, one-seeded. There is only one species; ri:. G. micranthus.
GONDOLA, in naval architecture, a flat kind of boat, very long and narrow, chiefly used on the canals at Venice.
GONG, in music, an instrument used in China, is made of a metal composed of silver, lead, and copper, and its shape is a sort of circular concave. The tone is loud, harsh, and clanging. It is never introduced except on occasion of giving a national cast to the music in which it is employed, or to awaken surprize, and rouse the attention of the company. •
GONIOMETRY, a method of measuring angles with a pair of compasses, and that without any scale whatever, except an undivided semicircle.Thus, having any angle.