ELASTIC CONSTANTS OF ROCKS. 
49 
Two sets of measurements for the elastic constants were made on a single 
square prism of the rock, using first one set of faces and then the other. The 
results are set forth in the following table : 
Nepheline Syenite, Montreal, Canada. 
No 
a 
a 
a 
a 
Size . 
1 X 1.003 
i 
1.003 
Area 
1.003 
1.003 
E 
9,230,000 
9,045,000 

(T 
.249 
.263 
D. 
6,125,000 
6,350,000 
.... 
C . 
3,695,000 
3,575,000 
Longitudinal compression (multiply readings 
by 4 for millionths). 
Lateral extension 
(millionths). 
Load (in pounds). 
Side 
U. 
Side 
P. 
Side 
U. 
Side 
P. 
1,000 
2 OOO 
O 
35 
70 
100 
135 
165 
200 
235 
270 
234 
200 
165 
I4O 
100 
70 
35 
5 

35 
65 
105 
135 
170 
205 
245 
275 
240 
2IO 
170 
140 
105 
70 
35 
2 
O 
25 
50 
80 
105 
130 
1 60 
185 
216 
190 
165 
135 
no 
85 
55 
30 
5 
O 
25 
51 
80 
no 
145 
175 
200 
2 3 
200 
1 80 
155 
125 
95 
65 
35 
5 
T, OOO 
4. OOO 
5 OOO 
6 ooo. . . . 
7 OOO. 
8,000 
Q.OOO. . 
8,000 
7,000. . 
6,000 
5,000 
4,000 
^,000. . 
2,000 
1,000 
The stress-strain curves obtained in the first set of measurements are seen 
in fig. 19 (p. 48), in which I represents longitudinal compression and II 
shows lateral extension. An examination of these will show that the rock 
exhibits very little hysteresis, the values for longitudinal compression giving 
a straight line, as in the case of wrought iron and other metals. 
The averages of the results obtained are as follows : 
=9,137,500; ff = 0.256; #=6,237,500; C= 3,635,000. 
The differences between the two determinations for the value of D amounted 
to only 225,000 pounds. As will be observed, the value of D for this rock is 
much higher than that for any of the granites. 
