36 



of Elasticity of Concrete as Determined by Tcste 

 Made at Watertown Arsenal in 1899. 



(10) That the coefficient of expansion of concrete 

 varies from 0.00000545 to 0.0000067 per deg. F. and that of 

 steel 0.00000617 to 0.00000676. 



(11) Invisible cracks appear in the concrete when the 

 ultimate strength of the concrete in tension is reached. 



(12) That the moment in a beam varies with the fol- 

 lowing variations in loading, as contained in Duel & Hill's 

 formulae: 



For a beam supported at both ends and loaded 



at the center with a load \V M = Wl+4 





