Adams and Colcer — Elastic Constants of Rocks. 113 



shows a distinct parallelism in the arrangement of the constitu- 

 ents, to which may be attributed a considerable divergence in the 

 results obtained in the different measurements of the elastic con- 

 stants. 



16. Olivine diabase, near Sudbury, Ontario, Canada ; a typical 

 line-grained, perfectly massive olivine diabase, occurring as a 

 large dike cutting rocks of Huronian age. 



Sandstones. 



IV. Sandstone, Cleveland, Ohio, U. S. A., a fine, even-grained 

 yellowish sandstone, extensively used for building purposes. The 

 bedding is marked by a slight variation in the color of the dif- 

 ferent beds. The prism used in the measurement of the elastic 

 constants was cut from a single bed and was taken parallel to the 

 plane of bedding. 



A summary of the results obtained in the measurement of 

 the elastic constants of these rocks is given on p. 121. The 

 extended results are here presented in the case of three rocks 

 only, which may serve as representatives of the others. 



Carrara Marble : 



Three specimens of the rock were used in measuring the 

 elastic constants, two squares prisms (a and b) and a round 

 column (<?). Two sets of measurements were made on both b 

 and c, the instrument as usual being affixed to the specimens 

 in two positions at right angles to one another in each case. 

 In this way five sets of measurements were made. The results 

 are set forth in the following table : 





Carrara Marble 







No. a 



b 



b 



c 



G 



Size 1*032 X 1*035 



1-017X1'016 







•985 



•985 



Area 1-07 



1033 



1-033 



•762 



•762 



E 8,120,000 



7,800,000 



8,055,000 



8,210,000 



8,045,000 



o- -281 



•274 



•273 



•275 



•269 



D 6,170,000 



5,750,000 



5,920,000 



6,100,000 



5,790,000 



C 3,170,000 



3,060,000 



3,160,000 



3,210,000 



3,170,000 



The averages 



of the results 



obtained for 



the respective con- 



stants are as foil 



ows : — 









.#= 8,046,000; 



cr=:0-2744; 



Z>=5,946,000 



; (7=3,154,000. 



The difference between the highest and lowest determina- 

 tions of D is 420,000 pounds. 



Figure 6 shows the stress strain curves plotted from the 

 results obtained from specimen a, the ordinates representing 

 the load (stress) and the abscissae the amount of the strain. I 



