TESTING OF WIRE. 



259 



to produce fracture. The initial tension on the wire should 

 be noted if possible. 



138. Tensile Tests of Wire. This test consists in break- 

 ing the wire under a tensile load, with or without a 

 measurement of the ultimate elongation. There are a great 

 variety of machines on the market for the purpose of testing 

 wires in tension. A simple form of the machine, previously 

 illustrated (Fig. 37), made by Messrs. Bailey, is largely 

 used on account of its ease of access and convenience 



FIG. 126. 



in handling. A useful single lever vertical machine, 

 made by Messrs. Denison, of Leeds, is shown on Fig. 

 126. The holding wedges are finely cut, and are 

 provided with the makers' patent arrangement by which 

 they are under control, and are both advanced, or both 

 receded together. This arrangement enables the wire to be 

 taken hold of very easily and quickly. The stretch of the 

 wire is taken up by a worm-wheel and rack gear, which is 



