IN INVESTIGATION INTO 
in values for Poisson's ratio, when measured in different directions. A simi- 
lar variation is also obtained with different specimens of the rock. The rock 
in fact, is not uniform and isotropic, so that, as has been mentioned, it is not 
one which is suitable for the application of the method employed in this paper, 
if accurate results are required. 
The figures obtained from the measurement of two specimens are given in 
the following table : 
Gabbro, New Glasgow, Province of Quebec, Canada. 
No 
b 
C 
b 
C 
Size 
.956 X .968 
1 X 1 . 022 
.968 
1 
Area 
.925 
1.022 
E 
12,300,000 
19,000,000 
a . 
.1985 
.24 
D 
6,810,000 
12,300,000 
c 
5,130,000 
7,600,000 
Longitudinal compression (multiply readings 
by 4 for millionths). 
Lateral extension 
(millionths). 
Load (in pounds). 
I OOO 

25 
50 
75 
105 
135 
1 60 
190 
220 
190 
165 
140 
no 
85 
60 
35 
9 

14 
29 
47 
59 
79 
94 
109 
129 
105 
95 
83 
60 
50 
30 
15 
o 

17 
33 
50 
67 
83 
83 
65 
55 
35 
20 
5 
o 
ii 
21 
32 
4 6 
61 
61 
45 
35 
25 
15 
2 
2 OOO 
3 ooo 
A OOO 
^ ooo 
6 ooo 
7,000. . 
8 ooo 
Q OOO 
8 ooo 
7 OOO. . 
6,000 '. . . 
5 ooo 
A OOO 
3,000 
2 OOO 
I, OOO 
As will be seen, D in one case is 6,810,000 and in the other 12,300,000. In 
figure 22 the stress-strain curves obtained by plotting the results of the meas- 
urement of prism b are given, and show a considerable permanent set, but 
comparatively little hysteresis. In this figure I represents longitudinal 
compression and II lateral extension. Prism c gives an equally good curve. 
It is quite probable that both are correct for their respective specimens. 
