292 



W. H. WARREN. 



four screws ; a spirit level is laid on the test piece while 

 it is being fixed in the machine, and set accurately in a 

 horizontal plane. A double set of Martens' mirror apparatus 

 is then attached, by means of which the elongations are 

 observed, using two reading telescopes and scales on each 

 side of the test piece. The elongations can thus be 

 measured to T oioo mm., or YreWir of an inch. In these 

 tests the elongations have been recorded for multiple of 

 •00004 of an inch. 



Tables I. and figs. 4, 5 and 6 give the results of testing 

 the mortars at ages varying from two to twelve months, 

 in which the coefficient, or modulus of elasticity, has been 

 calculated at stresses varying from about 50 lb. per square 

 inch to as nearly as possible the breaking stress. Table II. 

 and figs. 7 and 8 give the results of testing similar pieces 



'00008 -00016 '00024 '00032 '0004 '00048 '00056 '00064 '00072 '0008 

 Extensions in inches. 



Fig. 4 — Tensile Tests of Mortar Briquettes. Age 12 months. 

 No. 1 — One Hemmoor Cement to two Emu Plains sand. 

 No 2 — „ „ three „ „ 



No. 3— „ „ four 



