134 



FORMS OF 



objection to this form is that the fracture is liable to 

 take place at a point not on the measured portion. 

 In some cases, where the full quantity of metal is not 

 available, much smaller specimens are employed, and the 

 measurements taken on shorter lengths, but it is always 

 advisable, where it can be done, to adhere to the 10 in. 

 length, if only for the sake of uniformity. Bars are 

 often tested with the skin on, the specimens being 

 simply lengths of about 1<S in., cut from the bar. This 



o 



I 



o 



FIG. 65. 



form is shown at D ; here the measurements are taken on 

 a 10 in. length, and about 4 in. are allowed at each 

 end for gripping purposes. In some cases the better 

 plan is adopted of taking a bar of the above length and 

 turning it down in the middle portion, as shown at E, the 

 ends being held in wedge grips ; by adopting this plan the 

 measuring portion is made perfectly uniform, and fracture 

 necessarily takes place here. Smaller round specimens, 



