4 6 
AN INVESTIGATION INTO 
from figure 17, which shows the results obtained in the first three cycles of 
compression made upon a column of the rock. The hysteresis shown is 
much greater than in the case of any of the other crystalline rocks 
examined, and even after repeated stressing this hysteresis, although reduced, 
does not disappear, as is seen from the curve of the results obtained from 
column a given in figure 18. In this figure I represents longitudinal com- 
pression and II lateral extension. The variation in the results obtained for 
D accordingly is high, amounting to 890,000. 
900O 
1000 
^OO 30O 
400 
500 
STRAIN 
600 
7OO 
800 
FIG. 17. Stress-strain curves obtained in the first three cycles of compression, from 
a column of Stanstead Granite, showing its imperfect elasticity. 
On account of its defective elasticity the result of the measurement of 
the compressibility of this rock is less satisfactory than that of the other 
granites, from which it differs considerably in the value obtained for D, 
although the values obtained in the case of the other granites agree pretty 
closely among themselves. The cause of this defective elasticity in the 
Stanstead granite is not clear, although it may be connected with a lack 
of strength in the rock, which in its turn may be connected with the presence 
in the rock of so large an amount of mica. 
It is a weak rock compared with other granites or with the essexite from 
Mount Johnson, as shown by the results of a series of tests carried out in the 
Testing Laboratory of McGill University, and given in the table on page 47. 
A color process photograph of a polished surface of the rock is shown in 
Plate X A, and the photomicrograph of a thin section of it in Plate X B. This 
