STATE GEOLOGIST. HU eI 
66. After 24 hours in moist air, the test pieces for longer periods 
of time should be immersed in water maintained as near 21° C. (70° F.) 
as practicable; they may be stored in tanks or pans, which should be of 
non-corrodable materials. 
TENSILE STRENGTH. 
67. The tests may be made on any standard machine. A _ solid 
metal clip, as shown in figure 81, is recommended. ‘The clip is to be 
used without cushioning at the points of contact with the test specimen. 
The bearing at each point of contact should be ™%4 inch wide, and the 
distance between the center of contact on the same slip should be 114 
inches. 
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Fig. 81. Standard form of clips for holding tensile test pieces. 
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a 
68. Test pieces should be broken as soon as they are removed from 
the water. Care should be observed in centering the briquettes in the 
testing machine, as cross-strains produced by improper centering tend 
to lower the breaking strength. The load should not be applied too 
suddenly, as it may produce vibration, ‘the shock from which often 
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