ELASTIC CONSTANTS OF ROCKS- 
Three square prisms of the rock were employed in measuring the elastic 
constants, and on these seven sets of measurements of vertical compression 
and six of lateral extension were made, as shown in the table on page 30. 
The averages of the results obtained are as follows: 
E= 9,006,000; *= 0.2513; D= 5,967,000; C= 3,607,000. 
The difference between the highest and lowest values obtained for D is 
360,000. As will be seen by consulting figure 9 the rock is almost free from 
hysteresis. In this figure I represents the longitudinal compression and II 
lateral extension. 
9000 
<0 7000 
^5000 
O 
300O 
IOOO&- 
I2O 160 200 240 280 
STRAIN 
40 80 
FIG. 9. Tennessee Marble. Stress-strain curves. 
FOSSILIPEROUS LIMESTONE (TRENTON FORMATION), MILE END QUARRY, 
MONTREAL, CANADA. 
This is a typical fossiliferous limestone of the Trenton formation (Ordo- 
vician) . It was taken from a massive bed 2 feet in thickness known as the 
"Lower Bed "at the quarry from which the greater part of the building stone 
for the city of Montreal is obtained. The rock is dark gray in color, and is 
compact and solid in character. 
Under the microscope it is seen to be composed of fragments of fossils 
which are in some cases angular and in others more or less rounded. They 
are chiefly bits of Monticulipora and of Crinoids and show the structure 
of these organisms perfectly. These fragments lie embedded in clear transpar- 
ent calcite, occurring as large individuals which form a continuous mosaic, 
giving rise in this way to a perfectly compact rock. 
A color-process photograph of a polished surface of this rock is given in 
Plate VA. A photomicrograph of a thin section of the rock, taken in ordinary 
