all these different fusions, the plate is beaten by a hammer wetted with water, and the proper length, breadth, and thickness, 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 six times, and the punches used each time, are progressively smaller. It is of importance that the plate never be heated beyond a cherry-red, because if it receives a higher degree of heat, the steel undergoes an unfavourable change. The plates, when finished, present a very hard material, which nevertheless will yield to the strokes of the punches and hammer, which they require when the holes become too much enlarged by the frequent passing of the wire through them.
" When the plates have been repaired several times, they acquire a degree of hardness which renders it necessary to anneal them, especially when they pm from one size to another ; sometimes they do not acquire the proper quality until they have been annealed several times. Notwithstanding all the pre cautions which are taken in preparing the plates, the steel still vanes a little in hardness, and according to this variation they should be employed for drawing either steel or iron-wire ; and if the workman who proves them finds that they " A plate that is best adapted for drawing of steel wire is often unfit for the iron ; for the long pieces of this latter metal will become smaller at the extre mity than at the beginning, because the wire, as it is drawn through the plate, is insensibly heated, and the adhering parts are swelled, consequently pressed and reduced in size towards the latter end. The plates that aro fit for brass are often too soft for iron, and the effect resulting is the reverse of that produced by a_plate that is too hard.
"The smallest plates which Messrs. Mouchel use are at the least two cen timetres. or eight-tenths of an inch, in thickness, so that the holes can be made sufficiently deep ; for when they are of a leas thickness they will seize the wire too suddenly, and injure it.
"This inconvenience is much felt in manufactories where they continue to use the plates for too long a time, as they become exceedingly thin after frequent repairs. One of Messrs. Mouchel's large plates reduces 1,400 kilogrammes (3,080 lbs. avoirdupois) from the largest size of wire to No. 6, which is of the thickness of a knitting-needle ; 400 kilogrammes (880 lbs.) of this number are afterwards reduced in one single small plate, to No. 24, which is carding-wire ; and to finish them, they are passed through twelve times successively. Wires are frequently drawn so fine as to be wrought along with other threads of silk, wool, or hemp ; and thus they become a considerable article in the manu factures."
" Dr. Wollaston, in 1813, communicated to the Royal Society, the result of his experiment,' in drawing wire. Having required some fine wire for telescopes, and remembering that Muachenbrock mentioned wire 500 feet of which weighed only a single grain, he determined to try the experiment, although no method of making such fine wire had ever yet been published. With this view, he took a rod of silver, drilled a hole through it only one-tenth its diameter, filled this hole with gold, and succeeded in drawing it into wire till it did not exceed the three or four-thousandth part of an inch, and could have thus drawn it to the greatest fineness perceptible by the senses. Drilling the silver be found very troublesome, and determined to try to draw platina wire, as that metal would bear the silver to be cast round it. In this he succeeded with greater ease, drew the platina to any fineness, and plunged the silver in heated nitric acid, which dissolved it, and left the gold or platina wire perfect." In 1819 a patent was taken out by Mr. Brockedon, for mounting the wire drawing plates with diamonds, sapphires, rubies, and other bard gems ; in these conical boles were to be drilled, with their extremities rounded oft; which were afterwards to be polished by the processes known to lapidaries. By these means it was expected the wire might be more equally and cylindrically drawn, owing to the impenetrable hardness of the gems, which would not sensibly wear from the same cause.
As the repeated annealings to which iron wire is subjected, to cause it to yield to the resistance of the draw-plate, would be destructive of the property from which steel derives its utility, steel wire, therefore, during the process of annealing, is surrounded with charcoal-dust from which carbon is reabsorbed in the furnace ; thus the metal is rendered very soft and yielding, without losing its steel property.
Among the curious and important "results of machinery" might be mentioned the manufacture and application of steel wire to the making of the hair-springs of watches. " A pound of crude iron costs one half-penny ; it is converted into steel ; that steel is made into watch-springs ; every one of which," it it said, "is sold for half a guinea, and weighs only the tenth of a grain, after deducting for waste, there are in the pound weight about 7,000 grains ; it therefore affords steel for 70,000 watch-springs, the value of which, at half a guinea each, is 35,000 guineas!" Now as there are 504 half-pence in a guinea, the pound of crude iron has increased 17,640,000 times in value.