Even when made with the greatest possible care, the holes of iron eed draw-plates will enlarge so much with wear as to render it impos sible to draw any very great length of wire perfectly uniform in thick ness. To remedy this, Mr. Brockedon obtained a patent in 1819 for making draw-plates, the holes of which consist of diamonds or other hard precious stones. Dr. Ure states that with a plate of this kind mounted with a ruby, pierced with a bole •0033 of an inch in diameter, a silver wiro 170 miles long has been drawn so perfectly uniform, that no difference could he detected either by weighing portions of equal length or by measuring with a micrometer.
Dr. Wollaston communicated to the Royal Society, in the year 1813, a method of drawing wire of extreme tenuity, suitable for use in micrometers. This he accomplished, in the first instance, by boring or drilling a rod of silver. longitudinally, with a hole one-tenth of its own diameter, and than filling it with gold. The compound bar being drawn into wire or With of an inch in diameter, the silver was afterwards dissolved in heated nitric acid, leaving a perfect gold wire or of an inch in diameter. Finding the operation of drilling the silver rod very troublesome, he subsequently drew platina wire, and cast the silver round it, treating the compound bar as before. Even by ordinary processes, brass wire is made so thin, that gauze may be woven from it e hich will have 67,000 meshes in a squ ere inch. '1 he extreme ductility of the precious metals is still more strikingly illustrated by the manufacture of what is commonly known as gold wire, but which is really formed of silver gilt, actual gold wire being made only for filagree-work and a few other purpose*. In the ordinary mode of making gold wire, a silver rod about an inch thick is covered with leaf-gold, and then extended to the required tenuity by successive drawings and anuerdings ; the proportion of gold allowed to a pound of silver being seldom more than 140 grains, and sometimes as little as I00 grains. Fine gold wire is used for wrapping or twisting round thread to form gold thread ; and its beauty is greatly increased, while it is enabled to cover a larger surface, by flattening it between polished steel rollers.
For making needles, cards for the woollen and cotton manufacture, and various other articles into which wire is fabricated, it is necessary to remove the ourvature which it receives by being wound upon the cyliudrical or conical drum above alluded to. This is done by drawing the wire between pins fixed iu a piece of wood, and so arranged as to bend the wire into a wavy line, the flexures of which gradually dimi nish until they disappear altogether, leaving the wire perfectly straight. The size of wire is commonly measured by means of a gage, which consists of a plate of steel with a series of deep notches or slits at each edge, varying slightly from each other in width, and numbered accord ing to the number given to wire of corresponding size.
Among the many uses to which wire is applied, the manufacture of wire-gauze or cloth is peculiarly interesting. Plainer kinds of weaving are performed by a modification of the common loom, the coarser varie ties of woven wire-work produced being used for fences, pheasantries, coarse riddles or sieves, ibe. ; while the finer sorts are employed for lan
terns, sieves, flour-dressing machines, paper -making machinery, win dow-blinds, itc. Aviaries, flower-trailing, skylights, garden borders, plant-guards, arbours and summer-houses, flower-bed canopies, flower stands, chairs, garden-seats, window-blinds, bird-cages, fire-guards and fenders, lamps and lanterns, meat-safes, lattice for book cases and windows, sieves and strainers, all are now made of wire. The property which renders wire-gauze so invaluable in the safety-lamp has been taken advantage of by the Chevalier Aldini for the construction of wire-armour for the use of firemen, which, though very light, is in a great measure flame-proof. Wire-gauze is also formed into dish-covers, baskets, and other useful and ornamental articles, by pressing it between moulds into the proper shape, which it retains permanently. After being pressed into the required form, the articles are strength ened and neatly finished off by the addition of hoops or rings to their edges before they are removed from the mould. Needle-making is one of the most important applications of steel wire. Some of the finest sorts of steel wire are made into wateh-springs, in which form they receive an augmentation of value beyond the prime cost of the mate rial probably unparalleled in the whole range of manufacturing indus try. Of the delicate hairlike springs alluded to, which weigh only one-tenth of a grain, 70,000 ara required to weigh a pound ; and it has been repeatedly stated, though perhaps now the statement may be hardly correct, that the value of such springs is half a guinea each ; so that while a pound of crude iron cost but one halfpenny, a pound of these delicate manufactured articles produced from it was worth 35,000 guineas. One of the most elegant applications of gold and silver wire is to the production of filagree or filigrane work. To form this, fine gold and silver wire, often curled or twisted in a serpentine form, and sometimes plaited, are worked through each other, and soldered together so as to form festoons, flowers, and various orna ments ; and in many places also they are frequently melted together by the blow-pipe into little balls, by which means the threads are so' entwisted as to have a most beautiful and pleasant effect. This kind of work is of great antiquity, and was formerly much employed for caskets, needle-cases, trinket-boxes, baskets, shrines, and various deco rations for church furniture ; but it tins in a great measure fallen into disuse. Spangles, or paillates, which are small round leaves of metal, pierced in the middle, and used for ornamenting garments, are also formed of wire. A piece of wire is twisted round a red like the thread of a screw, and then cut into little spiral rings, each of which, being laid on a smooth anvil, is flattened by a hammer into the fonn.of spangle.
An important purpose to which iron wire has been recently applied is in the manufacture of ropes, which are very superior iu strength to those made of hemp, weight for weight. An account of wire ropes is given under Rom-Magi:so, and of wire bridges under BRIDOE.