TABLE 83. 

 ELASTICITY OF CRYSTALS. 



I0 3 



Some particular values of the Elastic Moduli are here given. Under E are given moduli for extension or compression 

 in the directions indicated by the subscripts and explained in the notes, and under T the moduli for torsional 

 rigidities round the axes similarly indicated. Moduli in grams per sq. cm. 



In the RHOMBOHEDRAL SYSTEM, Voigt has measured quartz. The subscripts have the 

 same meaning as in the hexagonal system. 



E = 1030X10, E_ 45 =1305X106, E +4 5 = 850X10, E 90 = 785X10, 



To = 508 X io 6 , T 90 = 348 X io 6 . 

 Baumgarten^T gives forcalcite 



E == 501 X io'\ E_ 45 = 441 X io' 1 , E + 45 = 772 X io 6 , E 9 o = 79 X io r> . 



* In this system the subscript a indicates that compression or extension takes place along the crystalline axis, and 

 distortion round the axis. The subscripts b and c correspond to directions equally inclined to two and normal to the 

 third and equally inclined to all three axes respectively. 



f Voigt, " Wied. Ann." 31, p. 474, p. 701, 1887; 34, p. 981, 1888; 36, p. 642, 1888. 



J Koch, " Wied. Ann." 18, p. 325, 1882. 



Uecketikamp, "Zeit. fiir Kryst." vol. io. 



li The subscripts i, 2, 3 indicate that the three principal axes are the axes of stress; 4, 5. 6 that the axe; 

 are in the three principal planes at angles of 45 to the corresponding axes. 



IT Baumgarten, " Poj-g. Ann." 152, p. 369, 1879. 

 SMITHSONIAN TABLES. 



