G O L

G 0 L

( 531 )

an inch wide. This plate is heated red hot,in order to bum off the tallow, and is then ex-tended by forging on an anvil, and afterwardspalled between fteel rollers, till it becomes along ribband as thin as paper. The ribbandis now cut into 150 equal pieces, each of whichis forged on an anvil, till it is about an inchfquare, after which they are well annealed. Eachof the fquares in this ftate weighs fix grains andfour tenths, and in thicknefs is equal to ofan inch. The 150 plates of gold thus produced,are interlaid with pieces of very fine vellumabout four inches fquare, and about twentyvellum leaves are placed on the outfides, thewhole is then put into a cafe of parchment,over which is drawn another fimilar cafe, fothat the packet is kept clofe and tight onall fides. Being now laid on a fmooth blockof marble, from 200 to 6oolbs. in weight, theheavier the better, the workman begins thebeating with a round-faced fomewhat convexhammer, called the cutch hammer, weighingfixteen pounds; the packet is turned occafio-nally upfide down, and beaten with ftrong butnot acute {brakes, till the gold is extended nearlyto an equality with the vellum leaves, to afeer-tain which the packet is opened from time totime, and alfo bent and rolled between thehands to facilitate the extenfion of the gold be-tween the leaves. This firft part of the procefsbeing compleated, the packet is then taken topieces and each leaf of gold is divided into fourwith a fteel knife; the 600 pieces thus pro-duced are interlaid with pieces of ox-gut, of thefame dimenfions and in the fame manner asthe vellum. The beating is continued, butwith a lighter hammer called the Jhoddering ham-mer, and weighing about twelve pounds, tillthe gold is brought to the fame dimenfions asthe interpofed membrane. It is now againdivided into four, by means of a piece of canecut to an edge, the leaves being by this time folight that any accidental moillure condenfingon an iron blade, would caufe them to adhereto it. The 2400 leaves hence refuldng areparted into three packets, with interpofed mem-brane as before, and beaten with th efinifiingor gold hammer, weighing about ten pounds,till they acquire an extent equal to the former.The packets are now taken to pieces, and thegold leaves, by means of a cane inftrument andthe breath, are laid flat on a leathern cufhion,and cut one by one to an even fquare, by a caneframe ; they are laftly laid in books of 25 leaveseach, the paper of which is previoufly fmoothedand rubbed with red bole, to prevent them from

adhering. Hence it appears that each of theinch-fquare pieces, into which the ribband ofgold was divided, is extended by beating to196 fquare inches, or 16 leaves, weighing 0.4.of a grain each, and not exceeding in thicknefsiToVis of an inch. Every grain of gold fur-nilhes 30.6 fquare inches.

Gold wire, as it is called, is in fa£l onlyfilver wire gilt, and is prepared in the followingmanner. A folid cylinder of fine filver weigh-ing about twenty pounds, is covered with thickleaves of gold which are made to adhere infe-parably to it by means of the burniflier: fuccef-five laminae are thus applied, till the quantityof gold, if intended for common gold wire,amounts to 100 grains for every pound troy offilver; if for double gilt wire, to about 140grains. This gilt filver rod is then drawnfuccellively through holes made in a ftrong fteelplate till it is reduced to the fize of a thickquill, care being taken to anneal it accuratelyafter each operation. The fucceeding procefsis fimilar to the former, except that a mixedmetal fomewhat fofter than fteel is employedfor the drawing plates, in order to prevent thegilding from being ftripped olF, and no furtherannealing is requifite after it is brought to be asflender as a crow-quill. When the wire is fpunas thin as is neceflary, it is wound on a hollowcopper bobbin, and carefully annealed by a verygentle heat: finally it is pafl'ed through, a flattingmill, and the procefs is compleat.

According to Dr. Halley, fix feet in lengthof the fineft gilt wire before flatting, willcounterpoife no more than a grain: and as thegold is not quite -jV of the whole, a Anglegrain of gold thus extended will be 345.6 feetlong. By the operation of flatting, the lengthof the wire is increafed about a feventh, andits width is equal to Vr of an inch: hence thefurface occupied by one grain is equal to 98.7fquare inches, with a thicknefs of of

an inch.

§ 6. Chemical properties of gold.

Gold requires for its fufion a low whiteheat equivalent to 3 2° of Wedgwood, or 1300of Fahrenheit, and in this ftate its furfaceappears of a luminous blueifh green colour.It expands lefs than mod metals by any additionof heat as long as it continues folid, but isenlarged more than any other during its paflagofrom folidity to fluidity, hence it ■ is peculiarlyunfitted to take a fharp impreflion from calling,and hence alfo it is very apt to prove brittle iffuddenly congealed, as by pouring into a coldmould. When divided into fmall parts, as3x2