Adams and Coker — Elastic Constants of Rocks. 115 



The averages of the values obtained 

 are as follows : 



E= 7,394,500 ; <r = '2195 ; 



D— 4,397,500; C = 3,019,700 



The difference between the highest 

 and lowest values in the four determina- 

 tions of D on specimen d was only 

 280,000. 



Of the other columns a gave on an 

 average somewhat lower and b some- 

 what higher results. 



The stress strain curves obtained from 

 specimen a are shown in figure 8. The 

 hysteresis is greater than that shown in 

 the case of any of the other granites 

 except that from Stanstead. 



In figure 9 the stress strain curves for 

 the Peterhead granite, and in figure 10 

 those for the nepheline syenite are 

 shown for purposes of comparison. 



Olivine Diabase, near Sudbury, Ontario, 

 Canada. 



Four test pieces were used in deter- 

 mining the elastic constants of the rock, 

 viz : three round columns and one nearly 

 square prism. They are designated as 

 a, b, c and d. The three round columns 

 were cut out of a block of the diabase 

 by means of an annular diamond drill. 

 Two measurements were made on each 

 of these in planes at right angles to one 

 another, in each case, while four meas- 

 urements were made on the prism d 

 using two pairs of faces. In this way 

 ten complete sets of measurements were 

 made for the elastic constants of this 

 diabase. 



The values obtained are given in the 

 tables on p. 117. 



As will be seen, the values obtained 

 for D in this rock are considerably higher 

 than those yielded by any other rock of 

 the series examined. In the six inde- 

 pendent measurements carried out on 

 the first three specimens, the difference 

 between the highest and lowest values 

 for D amounted to 830,000 pounds, 

 while on the four measurements made 

 on specimen d there is a rather greater 

 difference amounting to 845,000 pounds. Iz'r7^^^1 b ^ ^ 











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