108 F, M. GUMMOW. 



In order to show that such elongations could be endured 

 by the concrete without affecting its strength materially, 

 a test was made with a piece of concrete cut out of the 

 concrete-iron prism after the removal of the iron, and it 

 withstood when subjected to direct compression a com- 

 pressive stress of 1646 lbs. per square inch, with a coefficient 

 of elasticity of 2,130,000 lbs. A block of plain concrete 

 similar in aggregates, but which had not previously been 

 used for test purposes, crushed with 1987 lbs. per square 

 inch and showed a coefficient of elasticity of 4,400,000 lbs. 



The observations made on a buoy of hollow iron 1\ inches 

 diameter ami filled with cement mortar, erected on a rock 

 at Gorle-Bian in Prance, supplies a striking example of 

 the ductility of cement mortar or concrete. The waves 

 bent the buoy to a radius of 1*8 feet measured from the axis 

 of the buoy. Upon cutting same open along its axis the 

 cement mortar was found to consist of bent pieces, which 

 were with the exception of a few abrasions, otherwise 

 intact, and whose deformations as regards displacement of 

 the fibres, amounted to 2*4 inches to the foot. From the 

 above data it is evident since the elongations in construc- 

 tions do never exceed *0035 inches per lineal foot, that the 

 concrete possesses the power of elongation sufficient for all 

 practical purposes. 



5. The combined materials are capable of acting as one 

 body in taking up stresses when subject to bending 

 moments. 



In order that this characteristic may be considered in its 

 entirety, it becomes necessary to deal first with some 

 stresses otherwise created, which considerably affect the 

 issue of this statement. The stresses referred to are 

 caused by the alteration of the volume of concrete. 



1. By contraction when hardening in air. 



2. By expansion when hardening in water. 



