AN INVESTIGATION INTO 
The curves represent the readings for longitudinal compression, and, as will 
be seen, after the first cycle of compression the rock did not return quite to its 
original position, but this imperfection in elasticity becomes progressively 
smaller in the subsequent loadings till in the fourth compression cycle the 
return is almost perfect and the hysteresis very small. 
Figure 1 1 shows the curves obtained by plotting the values secured from 
the measurement of the elastic constants of specimen b after the state of ease 
had been induced, and if the curve for longitudinal compression in this be com- 
pared with that shown in figure 12 the great improvement in the elasticity 
of the rock will at once be seen. In figure 1 1, I represents longitudinal com- 
pression and II lateral extension. 
9000 
IOOO 
500 
900 IOOO 
600 700 800 
STRAIN 
FIG. 12. Stress-strain curves obtained in the first four cycles of compression from 
a column of Baveno granite, showing the progress toward a state of ease. 
GRANITE, PETERHEAD, SCOTLAND. 
A pink granite which is almost indistinguishable from the Lily Lake granite 
in hand specimens or polished blocks. In the thin sections also the resemblance 
is very close. The description given of the Lily Lake granite would also 
apply to this rock, except that the Peterhead granite contains rather more 
plagioclase and less biotite. The microperthite also is more turbid, indicating 
greater alteration. The quartz and microperthite which make up the greater 
part of the rock have evidently crystallized out at about the same time, 
since they have equally good crystalline outlines and impress their form upon 
each other with about equal frequency. The quartz usually shows pronounced 
undulatory extinction. 
Owing to its practical identity with the Lily Lake granite, in appearance and 
composition, it has been considered unnecessary to give either a photograph 
of the polished surface of the rock or a photomicrograph of a thin section. 
