WIRE-ROPE 



1151 



wire-drawn. The piece of steel called the draw-plate is pierced with a regular grada- 

 tion of holes, from the largest to the smallest; and the machine for overcoming the 

 lateral adhesion of the metallic particles to one another is called the draw-bench. The 

 pincers which lay hold of the extremity of the wire, to pull it through the successive 

 holes, are adapted to bite it firmly, by having the inside of the jaws cut like a file. For 

 drawing thick rods of gilt silver down into stout wire, the hydraulic press lias been 

 had recourse to with advantage. 



Fig. 2117 represents a convenient form of the draw-bench, where the power is ap- 

 plied by a toothed wheel, pinion, and rack-work, moved by the hands of one or two 

 men working at a winch ; the 

 motion being so regulated by a 2117 



fly-wheel, that it does not proceed 

 in fits and starts, and cause in- 

 equalities in the wire. The metal 

 requires to be annealed, now and 

 then, between successive draw- 

 ings, as otherwise it would become 

 too hard and brittle for further 

 extension. The reel upon which 

 it is wound is sometimes mounted 

 in a cistern of sour small beer, 

 for the purpose of clearing off, or loosening at least, any crust of oxide formed in the 

 annealing, before the wire enters the draw-plate. 



When, for very accurate purposes of science or the arts, a considerable length of 

 uniform wire is to be drawn, a plate, with one or more jewelled holes, that is, filled 

 with one or more perforated rubies, sapphires, or chrysolites, can alone be trusted to, 

 because the holes even in the best steel become rapidly wider by abrasion. Through 

 a hole in a ruby 0'0033 of an inch in diameter, a silver wire 170 miles long has been 

 drawn, which possessed at the end the very same section as at the beginning : a result 

 determined by weighing portions of equal length, as also by measuring it with a 

 micrometer. The hole in an ordinary draw-plate of soft steel becomes so wide, by 

 drawing 14,000 fathoms of brass wire, that it requires to be narrowed before the ori- 

 ginal sized wire can be again obtained. 



Wire, by being diminished one-half, one-third, one-fourth, &c., in diameter, is aug- 

 mented in length respectively four, nine, sixteen times, &c. The speed with which it 

 may be prudently drawn out depends upon the ductility and tenacity of the metal ; 

 but may be always increased the more the wire becomes attenuated, because its par- 

 ticles progressively assume more and more of the filamentous form, and accommodate 

 themselves more readily to the extending force. Iron and brass wires, of 0'3 inch in 

 diameter, bear drawing at the rate of from 12 to 15 inches per second ; but when of 

 4 025 (5*5) of an inch, at the rate of from 40 to 45 inches in the same time. Finer 

 silver and copper wire may be extended from 60 to 70 inches per second. 



By enclosing a wire of platinum within one of silver ten times thicker, and drawing 

 down the compound wire till it be ^g of an inch, a wire of platinum of g^ of an inch 

 will exist in its centre, which may be obtained apart, by dissolving the silver away in 

 nitric acid. This pretty experiment was first made by Dr. Wollaston. 



The French draw-plates are so much esteemed, that one of the best of them used to 

 be sold in this country for its weight in silver. The holes are formed with a steel 

 punch ; being made large on that side where the wire enters, and diminishing with a 

 regular taper to the other side. 



WIRE-ROPE. The manufacture of ropes made of wire has, of late years, become 

 a most important one. Not only are ropes of this description now employed in the 

 most extensive coal mines of this country, and for winding generally, but they are 

 used for much of the standing rigging of ships, and for numerous ordinary pxirposes. 

 Perhaps the most important application of wire-rope has been, however, in the con- 

 struction of the electric cables. See ELECTRO-TELEGRAPHY. 



The Tables on the following page show the relative values of ropes of hemp, iron, 

 and steel. 



The applications of wire are extraordinarily numerous and interesting. Many 

 thousands of lives are every day trusted to wire in the form of wire-rope for 

 collieries and mines, and the lives of the men ascending and descending a coal pit 

 literally depend from these iron threads. The standing rigging of ships is now gene- 

 rally made of wire-rope. The introduction of telegraphy has given great development 

 to the manufacture of wire. The conducting portion of submarine electric tele- 

 graph cables is simply a wire-rope made of copper wires, while the outside pro- 

 tective sheathing generally consists of iron wire. One of the most important appli- 

 cations of wire of late years is that of steel wire in the form of the wire-rope used for 



