598 FRANK D. ADAMS AND J. AUSTEN BANCROFT 



The sense in which certain terms are used in this quotation is 

 not quite clear, but we understand the question put forward by 

 Dr. Gilbert to be as follows: 



A unit cube of any rock — granite for instance — is submitted to 

 pressure in a testing machine on the earth's surface. It will give 

 away or break down under a certain load — this is termed its crush- 

 ing load. 



If this cube of rock were imbedded deep within the earth's 

 crust, great pressure would be exerted upon it from all sides. Such 

 being the case, and omitting from consideration the influence of 

 temperature, would the rock (i) be reduced to a condition which 

 approaches fluidity and move at once if the pressure in one direc- 

 tion became slightly greater than that in another ? Or (2) would 

 the rock become deformed only when this additional pressure in 

 one direction was equal to its crushing load at the surface? Or 

 (3) would the rock show an increased resistance to deformation and 

 require a much greater additional pressure in one direction to 

 deform it than was required to crush it at the surface ? 



A few preliminary trials which served to open up the experi- 

 mental investigation of this problem were undertaken some years 

 ago by Dr. Adams in association with Dr. Ernest G. Coker, then 

 Associate Professor of Civil Engineering at McGill University. 

 Dr. Coker subsequently resigned his position at McGill University 

 to accept the professorship of mechanical engineering and applied 

 mathematics at the Finsbury Technical College in London, and for 

 a time the work was discontinued. Dr. Bancroft, however, some 

 years later coming to McGill University, the investigation was 

 resumed. It has extended over a period of several years. The 

 writers desire to acknowledge their indebtedness to the Carnegie 

 Institute of Washington, the work having been carried out under 

 a grant received from that body. 



ROCKS EXAMINED 



The following rocks were examined: 

 White alabaster, Castelino, Italy. 

 White marble, Carrara, Italy. 

 Black Belgian marble ("Noir fin"). 



