1895.] Strains in the Testing of Materials and Structures. 121) 



Fio. 4. 





apart. When the instrument has been put in place, and the clip 

 screws tightened up, the nut J is released, P comes into gear, and 

 things are ready for the observation to be taken. 



The following are examples of tests made with the author's exten- 

 someter in its laboratory form. The pieces were loaded, in tension, 

 by means of the 50-ton Wicksteed single-lever testing machine of the 

 Cambridge Engineering Laboratory. The machine is worked by a 

 hydraulic intensifier, which affords a particularly convenient means 

 of varying the load gradually without shock and without setting the 

 weigh- beam into oscillation. Except when otherwise stated, the 

 increments of load were made at intervals of about one minute, that 

 interval sufficing for the adjustment of the load to a new value, and 

 for reading the extensometer. The unit of the exteusometer scale 

 readings is in all cases s-o(re inch. 



(1.) Turned bar of mild steel. Diameter, 1*249 inches. Length 

 under measurement, 8 inches. Temperature, 57 F. Zero of exten- 

 someter set at 400. Results of three successive loadings within the 

 elastic limit : 



L 2 



