[WHEELER] THERMAL EXPANSION OF ROCK 29 
was extinguished and the freezing point of the metal taken, the molten 
metal being stirred with the porcelain tube containing the hot junction, 
which stirring tends to prevent supercooling. The following results were 
taken as the most reliable for plotting the temperature curve for getting 
the temperature directly from the bridge readings, and a curve was 
drawn through the points by means of a flexible spline. (See also 
Figure III.) 
Bridge Divisions. Temperature. 
2.3 DE ig Ten ee DIN RUN ONE 152° C 
DOr Rass RUSSE RENE Ih VODA ART 10) AIR 
TS SOMMAIRE EN eee 445.8 
DRANG We ans AL OURS ASE ODA 
445 .4 SMR goa ares 962. 
After a few preliminary readings on a cylinder of diabase which 
had previously been heated, readings on a fresh olivine diabase from 
near Sudbury, Canada, were begun. A description and photographs 
of this diabase are given in “ An Investigation into the Elastic Constants 
of Rocks, More Especially with Reference to Cubic Compressibility”’ 
by Dr. Adams and Dr. Coker (published by the Carnegie Institution of 
Washington, D.C.) pp. 57-60. It is a “very typical fresh olivine 
diabase.” It is described as being rather coarse in grain but finer than 
any of the granites described in the above mentioned work, with the 
exception of the granite from Westerly, R.I., U.S.A. “The rock is 
perfectly massive and possesses a typical ‘ophitic’ or ‘diabase’ struc- 
ture.” 
The length of the cylinder before heating, measured with a pair of 
vernier calipers, at a room temperature of 18.3°C. was found to be 19.831 
ems. 
For the calibration of the micrometer microscopes, the approxi- 
mate mean of several calibrations, which had been obtained by de- 
monstrators in the Elementary Physics Laboratory of the Macdonald 
Physics Building, were taken; Microscope No. 1 being taken as 9.750 
turns to 1 mm. and No. 3 as 11.760 turns to 1 mm. 
The diabase cylinder was heated six times to about 1000°C., readings 
being taken at intervals during the heating and also during the cooling. 
The table of both the readings and the results will be given for the first 
heating and cooling as illustrative of the method of procedure; then 
simply the results of the other five heatings will be given. In columns 
one and two, the numbers given in parentheses are not micrometer 
microscope readings, but are the differences of the preceding and the 
