296 



W. H. W AH REN. 



* 



i 



40 - - - 



Fiq/4 



~^ 



y 



and the shortenings of the prisms under compressive stress 

 were measured by means of the Martens' mirror apparatus 

 in a similar manner to that described in the tension 

 tests (Fig. 10). The tests were all made in a vertical 



Fig. 10 — Shewing Compressive Test Piece in large Testing Machine 

 with Martens' Mirrors attached. 



testing machine, and the prisms were of similar composition 

 in regard to Portland cement and sand as in the tension 

 tests. The results are recorded in Table IV. and in figs. 11 

 to 13. 



