I Is 



TENSION TESTING. 



the ten inches between the two gauge marks. On this 

 diagram, the numbers along the base represent the number 

 of the inches from one end, and the vertical distances to the 

 diagram represent the extension on these inches. 

 The actual figures are as follow : 



8 IO 12 14 

 S.OA0S 



FIG. 68. 



2O 22 24 26 



89. Plotting the Diagram. It is often necessary and con- 

 venient to preserve a graphic record of a test, or, in other 

 words, to plot a complete diagram of the test. In educa- 

 tional testing this should always be done. It gives the 

 student an insight into the properties of the material he 

 has tested, which cannot be obtained by a mere inspection 



