144 W. H. WARREN. 



per inch, whereas if slipping had not occurred the extension 

 would have been only '0003972 inch per inch. 



Tables I. and II. give the coefficient of elasticity for 

 various stresses, and the curves Figs. I. a. and I. b., Figs. 

 II. a. to II. f. show the total loads applied and the extens- 

 ions produced by them. The decrease in the coefficient of 

 elasticity, as the intensity of stress increases, is charac- 

 teristic of reinforced concrete, and is clearly indicated by 

 the tables and curves. The coefficient of elasticity is the 

 tangent of the slope of the curve for the stress in question. 

 The column E = gggffJS necessarily differs from the 

 coefficient of elasticity, and it is given in order to supply 

 data for calculations on the transverse strength of beams. 

 The adhesion per square inch is calculated by measuring 

 the area of the surface of the rods, after the fracture of 

 the test piece, between the fracture and the extremity of 

 the head, and dividing this area into the total pull sustained 

 by the rods. The total pull on the rods is easily found from 

 the extension of the test piece, and the coefficient of 

 elasticity of the metal provided slipping has not occurred, 

 or it can be found by subtracting the pull on the unreinforced 

 material from the total load applied. Values of the adhesive 

 strength are given in Tables I. and II. approximately as 

 the actual tensile strength of the concrete itself in the 

 reinforced test piece is only approximately known. 



Compression Tests. — The results of a considerable number 

 of tests of mortar prisms 12 inches long by 6 inches by 6 

 inches of various proportions of cement to sand are 

 recorded in a previous paper. 1 



Table III. and Fig. III. a. give the results of testing 

 similar prisms of mortar, but at ages of from 720 to 729 

 days. The results do not differ to any extent from those 

 recorded on pages 306-7, l and show the diminution of the 



1 Journ. Koy. Soc. N.S. Wales, Vol. xxxvi., page 295. 



