ELASTIC CONSTANTS OF ROCKS. 
The figures obtained from one of these glass rods approximately an inch in 
diameter are given in the following table : 
Glass Rod. 
Size 
985 
97 
Area 
774 
E 
8 075 000 
(f 
.2 
D . . . 
4,485 000 
C 
3,361,000 
Load (in pounds). 
Longitudinal 
compression 
(multiply 
readings by 4 
for millionths). 
Lateral 
extension 
(millionths) . 
1,000 
2,000 
~\ ooo 

55 
qc 
O 
32 
61 
4 OOO 
I4S 
QC 
5 OOO 
2OO 
12T. 
6 ooo 
2 SO 
ice 
J OOO 
"*oo 
8,000 
^so 
Q.OOO . . 
8,000 
^so 
7 OOO 
70S 
6 ooo 
2 co 
I C. C. 
5 OOO 
2OS 
T 2 ? 
4 OOO . 
1 60 
1 P 
IOO 
3,000 
2,000 
I, OOO 
H5 
65 
5 
65 
35 
2 
That the tension in this glass seriously affected the results obtained as 
might be expected is clearly seen in the value for D being much too low, as 
will be shown later. 
9OOO 
7000 
5000 
3000 
/000< 
80 
120 
24O 
160 200 
STRAIN 
Glass Rod. Stress-strain curves. 
280 
320 
360 
FIG. 25. 
The stress-strain curves plotted from these values are shown in figure 25. 
As will be seen, the material exhibits a distinct hysteresis. 
