WIRE. 



as may be drawn by hand. The fteel which they employ 

 for thefe drawing-plates fhould never vary in quality, ex- 

 cept that the fmaller plates are made of the fineft fteel. 

 Several pieces of iron are difpofed in the furnace in the 

 form of a box without a lid, their weight being according 

 to the ufe for which they are intended to be employed. 



The workman fills each of thefe boxes with caft fteel, 

 and having covered it over with a luting of clay, it is ex- 

 pofed to a fierce fire until the fteel be melted. His art 

 confifts in feizing the proper moment to withdraw the plate 

 from the fire : he raifes the luting, and blows on it through 

 a tube, in order to drive off" all heterogeneous parts, and 

 then amalgamates it with the iron by light blows. After it 

 is cool, he replaces it at the fire, where the fufion again takes 

 place, but to a lefs degree than before ; he afterwards 

 works the fteel with light blows of the hammer, to purify 

 and folder it with the iron. This operation is repeated 

 from feven to ten times, according to its quality, which 

 renders it more or lefs difficult to manage. During this 

 procefs, a cruft forms on the fteel, which is detached from 

 it the fifth time of its expofure to the fire, becaufe this cruft 

 is compofed of an oxydated fteel of an inferior quality. 

 It fometimes happens that two and even three of thefe 

 crufts are formed of about two millimetres, or one-fixteenth 

 of an inch in thicknefs, which muft alfo be removed. 



After all thefe different fufions, the plate is beaten by a 

 hammer wetted with water, and the proper length, breadth, 

 and thicknefs, are given to it. When thus prepared, the 

 plates are heated again, in order to be pierced with holes by 

 punches of a conical form ; the operation is repeated five or 

 fix times, and the punches ufed each time are progreffively 

 fmaller. It is of importance that the plate never be heated 

 beyond a cherry-red, becaufe if it receives a higher degree 

 of heat, the fteel undergoes an unfavourable change. The 

 plates, when finiftied, prcfent a very hard material, which 

 neverthelefs will yield to the ftrokes of the punches and the 

 hammer, which they require when the holes become too 

 much enlarged by the frequent paffing of the wire through 

 them. 



When the plates have been repaired feveral times, they 

 acquire a degree of hardnefs, which renders it neceflary to 

 anneal them, efpecially when they pafs from one fize to 

 another ; fometimes they do not acquire the proper quality 

 until they have been annealed feveral times. Notwithftand- 

 ing all the precautions which are taken in preparing the 

 plates, the fteel ftill varies a little in hardnefs, and accord- 

 ing to this variation they fhould be employed for drawing 

 either fteel or iron wire ; and if the workman who proves 

 them finds that they are too foft for either the fteel or iron, 

 they are put afide, to be ufed by the brafs-wire drawers. 



A plate that is beft adapted for drawing fteel-wire is 

 often unfit for the iron ; for the long pieces of this latter 

 metal will become fmaller at the extremity than at the be- 

 ginning, becaufe the wire as it is drawn through the plate is 

 infenfibly heated, and the adhering parts are fwelled, confe- 

 quently preffed and reduced in fize towards the latter end. 

 The plates that are fit for brafs are often too foft for iron, 

 and the effect rcfulting is the reverfe of that produced by a 

 plate that is too hard. 



The fmalleft plates which Meffrs. Mouchel ufe are at the 

 leaft two centimetres, or eight-tenths of an inch in thick- 

 nefs, fo that the holes can be made fufficiently deep ; for 

 when they are of a lefs thicknefs, they will feize the wire 

 too fuddenly and injure it. This inconvenience is much 

 felt in manufaftories where they continue to ufe the plates 

 for too long a time, as they become exceedingly thin after 

 frequent repairs. One of Meffrs. Mouchel's Large plates 

 3 



reduces 1 400 kilogrammes (3080 pounds a-voirdupois) frons 

 the largeft fize of wire to No. 6, which is of the thicknefs 

 of a knitting-needle ; 400 kilogrammes (880 pounds) of this 

 number are afterwards reduced in one fingle fmall plate to 

 No. 24, which is carding wire ; and to finilh them, they are 

 paffed through twelve times fucceffively. 



For the tenacity of iron wire, fee Iron. 



The firft wire-mill in England was fet up by a Dutch- 

 man at Sheen, near Richmond, in 1663. 



Wires are frequently drawn fo fine, as to be wrough' 

 along with other threads of filk, wool, or hemp : and 

 thus they become a confiderable article in the manufac- 

 tures. See Ductility. 



Wire, Gold. See GoLU-lVire. 



Mufchenbroeck records, that an artift of Augrtjurg drew a 

 wire of gold fo flender, that 500 feet of it weighed onlj 

 one grain ; and Dr. Wollafton, fecretary of the Royal So- 

 ciety, has (hewn, that a wire of gold may be drawn much 

 finer than this, and that wires of platiiia may be drawn much 

 more flender, with the utmoft facihty. Thofe who draw filver- 

 wire in large quantities for lace and embroidery, fometimes 

 begin with a rod that is about three inches in diameter, and 



ultimately obtain wires that are fo fmall as of an inch in 



•' 100 



thicknefs. If in any ftage of this procefs a rod of filver-wire 

 be taken, and a hole be drilled through it longitudinally, 

 having its diameter one-tenth part of that of the rod, and if 

 a wire of pure gold be inferted, fo as to fill the hole, it is 

 evident that by continuing to draw the rod, the gold within 

 it will be reduced in diameter exaftly in the fame propor- 

 tion as the filver ; fo that if both be thus drawn out 



together till the diameter of the filver is of an inch, then 



that of the gold will be only ; and of fuch wire, 550 



feet would be requifite to weigh one grain. In order to re- 

 move the coating of filver that furrounds it, the wire muft 

 be fteeped for a few minutes in warm nitrous acid, which 

 diffolves the filver without any injury to the gold. Dr. W., 

 in his endeavours to make flender gold- wires by the method 

 above-defcribed, found it difficult to drill the central hole 

 in a metal fo fine as filver, and therefore tried whether pla- 

 tina might not be fubftituted for the gold, as in that cafe its 

 infufibility would allow its being coated with filver, with- 

 out the neceffity of drilling. Having formed a cyhndrical 

 mould one-third of an inch in diameter, he fixed in the centre 



of it a platina wire previoufly drawn to the — - of an inch, 



'^ "^ ' 100 



and then filled the mould with filver. When this rod was 



drawn to — , his platina was reduced to — — , and by fuc- 

 30 1000 



eeffive reduftion he obtained wires of 



and , and 



4000 5000 



excellent for applying to the eye-pieces of aftronomical in- 

 ftruments, and perhaps as fine as can be ufeful for fuch pur- 

 pofes. The extremity of a platina wire having been fufed 

 into a globule near 5 of an inch in diameter, was next ham- 

 mered out into a fquare rod, and then drawn again into a 



wire of an inch in diameter. The fufion was effefted 



253 

 by the following fimple and eafy method fuggeftcd by Dr. 



Marcct : 



