ORDINARY MEETINGS. Sk 
rubber no doubt differed in degree of vulcanisation from Mr. Macdonald’s, 
and as he used a different initial stress, it is not surprising that the elon- 
gations giving a minimum value for Young’s Modulus should be 0.25 in 
the one case and 0.5 in the other 
Mallock’s mean value of Young’s Modulus, when expressed in 
absolute C. G. S. units, was 8.56 x 10® for soft grey india-rubber, and 
34.16 x 10° for hard grey rubber. Asin the case of the rigidity, Mr. 
Macdonald’s values are intermediate, being nearer Mallock’s values for 
the soft than for the hard specimen. 
(2) The following table contains the determinations made for the 
second purpose mentioned above. 
Original Stress trae I Elongation per mone 
(grms. per sq. (grms. per sq. unit length. (abs. C. G. S. 
cm.) | cm.) mudi): 
First SERIES. 
1354 789 .0618 12.53 
2143 785 .0765 10.06 
2928 855 | .0955 8.78 
3783 | 995 .0816 WH 7 
4778 | 1072 .1152 9.13 
5850 | 1161 .0943 12.08 
SECOND SERIES. 
1397 784 | .0681 11.30 
2181 847 .0798 10.42 
3028 889 .0981 8.89 
3917 957 .0812 IL 5} 
4874 1036 .0829 12 26 
5910 1026 .0716 14.05 
Proc. & Trans. N.S. Inst. Sci., VOL. X. Proc,--C. 
