KENNEDY EXTENSOMETER. 



115 



is given by the reading of the vernier, and this can- be 

 compared with the reading given by the pointer on the 

 scale, and in this way the latter can be adjusted. The 

 best way of doing this, having graduated the scale so as 

 to give approximately the correct readings, is to move the 

 scale inwards or outwards until the reading exactly coin- 

 cides with the vernier reading. The length of the pointer 

 can then be adjusted to suit the scale. 



65. Kennedy Lever Extensometer for Vertical Bars.* 

 In addition to the extensometer which has just been 





FIG. 45. 



described, Dr. Kennedy has designed and used a somewhat 

 modified form, based upon the same principle, and suitable 

 for use on specimens which are held vertically, as well as 

 horizontally, in the machine. The design is simple, and 

 will be easily appreciated on reference to Fig. 45. Here A B 

 is the test bar ; C C is a rigid, right-angled frame, carrying 

 at its outer end a graduated scale S, and, at; the lower end of 

 its vertical arm, a centre point, which is held by means 



* Min. Proc. last. C.E., Vol. Ixxxviii. 



