108 Adams and Coker — Elastic Constants of Rocks. 



practically parallel. The differences between the readings 

 given by the same load at different temperatures were no 

 greater than those obtained by different measurements under 

 the same load at the same temperature. The conclusion there- 

 fore seems to be indicated that a change of temperature made 

 no perceptible difference within the range of temperatures em- 

 ployed, although a difference of 0*5 per cent, for each degree 

 centigrade would mean a difference of about 25 per cent in 

 range of temperature employed by Mr. McKergow. 



While therefore this experiment cannot be considered as 

 supplying accurate information concerning the effect produced 

 by a rise in temperature on the elastic constants of rocks, for 

 the instruments themselves are in some measure affected by 



Detail of hole 



3 mm 



Hole 



%h 



Fig. 4. Square test specimen of rock. Fig. 5. Eound test specimen. 



the same changes of temperature, yet they serve to show that 

 in the case of the massive crystalline rocks, the influence of 

 temperature is probably not very great. 



The Method of Measurements. 



In carrying out the measurements, prisms of the rock 1 inch 

 square and 3 inches long were usually employed (see lig. 4\ 

 These were cut and ground with smooth faces but were not 

 polished. In these two small round holes were drilled in the 

 medial line of each vertical face for the purpose of attaching 

 the instrument, when Young's modulus was to be measured. 

 These holes were made by means of a small diamond drill and 

 were perfectly round and smooth. They were each 0*05 to 



