Adams and Coker — Elastic Constants of Rocks. 107 



direct and simple method which, has been employed in the 

 present paper. These results bearing on the variation of elasti- 

 city induced by changes of temperature, especially in view of 

 the fact that they are stated by the investigators to be " pre- 

 liminary," can as yet hardly be taken as. of general application 

 to all rocks, even if correct for the specimen of sandstone 

 examined.* 



In onr own investigations the laboratory was maintained 

 at a temperature of from 63° to 6S° F. (17'2° C. to 20° C.), and 

 a thorough investigation into the effect of temperature was 

 not undertaken, as this would be very difficult to carry out 

 when employing the method of direct compression used, the 

 difficulty consisting in heating the specimen itself without in 

 any way affecting the measuring apparatus attached to it. 



It seemed, however, possible to ascertain whether any serious 

 change in the elastic constants of the massive crystalline rocks 

 employed in the present investigation would result from a 

 •moderate change of temperature. For purposes of trial the 

 rock selected was the Sudbury diabase, a typical fine-grained 

 plutonic rock. A column of it was placed by Mr. Mclvergow 

 in a small testing machine, having a capacity of 50 tons, and 

 the temperature of the room in which the machine was set up 

 having been lowered to +10° F. a cycle of compression read- 

 ings was taken in the usual way adopted when Young's 

 modulus is to be determined. The temperature of the room 

 was then raised by about 10° and another cycle of readings 

 was taken. It was then raised another 10° and a third series 

 of readings was obtained, and so on through successive stages 

 of 10° until the normal temperature of the room (about 65° F.) 

 was reached. The initial reading of the instrument before 

 the application of pressure was of course different in each case, 

 owing to the expansion of the rock which followed from heat- 

 ing. These initial points were plotted on a line, and the 

 results obtained when this specimen was subjected to a certain 

 maximum load, together with the increase of temperature at 

 each stage, were plotted on a second line. If the compression 

 was greater at 65° than at 10° for the same load, these two 

 lines should have diverged, but as a matter of fact they were 



*In two very interesting papers, received while the present paper was in 

 press (Modulus of Elasticity of Rocks and some inferences relating to Seis- 

 mology, Journal of College of Science, Imperial University of Japan, vol. xx, 

 article 9, 1905 ; and Kinetic Measurements of the Modulus of Elasticity, etc., 

 ditto, vol. xx. article 10, 1905), Kusakabe shows that the presence of moisture 

 in a rock has a very marked influence in diminishing its modulus of elasticity. 

 This influence, he has ascertained, is very much more pronounced in the case 

 of porous rocks — such as sandstone — which absorb a large quantity of water, 

 than in the case of the compact crystalline rocks. He suggests that the 

 effect, which in the paper above mentioned was attributed to heat, may 

 really be due to the presence of moisture. He is now engaged in investiga- 

 ting the influence of moisture combined with a high temperature upon the 

 modulus of elasticity of various rocks. 



