Table 83. 



ELASTICITY OF CRYSTALS. 



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. 



(a) Regular System. 



Substance. 



Fluor spar 

 Pyrites . . 

 Rock salt . 



Sylvine . . 



Sodium chloride 

 Potash alum . 

 Chrome alum 

 Iron alum . . 



M73 



3530 



416 



403 



401 



372 



405 

 iSi 

 161 

 186 



73 X io« 



X io« 

 X io« 

 X io« 

 X 10" 

 X io« 

 Xio« 

 X106 

 Xio*-' 

 X io« 



looS 



2530 

 346 



339 

 209 



196 



319 

 199 



177 



Xio« 

 X 10'' 

 X io« 

 X 106 

 X io« 

 X 106 

 X106 

 X106 

 Xio« 



E, 



910 X 10" 



2310 X 10*' 



311 X lo** 



345X106 



1075 X 106 



129 X 10^ 



655 X 10" 



Authority. 



Voigt.t 



Koch.J 



Voigt. 

 Koch. 

 Beckenkamp.§ 



(d) Rhombic System.]! 



Substance. 



Barite 

 Topaz 



El 



620 X 106 

 2304 X 10*^ 



540 X lo** 

 2S90 X 10'' 



959 X iqS 

 2652 X 10^ 



376 X lo" 

 2670 X 10'' 



702 X 106 

 2S93 X 10'^ 



740 X iqO 

 3180 X 10^ 



Authority. 



Voigt. 



Substance. 



Barite 

 Topaz 



Ti 2 = T, 



283 X 10'' 

 1336 X io"5 



Ti 3 — T3 1 



293 X 10^ 

 1353 X loe 



Til Q — T«> 



121 X 10'' 

 1 104 X 10*5 



Authority. 



Voigt. 



In the Mo.NOCLiNic System, Coromilas (Zeit. fiir Kryst. vol. i) gives 



GvDsum ^ ^"^ ^^ ^^7 X 106 at 21.9° to the principal axis. 

 ■JE^in^ 313X106 at 75.4° 



; = 2213 X 106 in the principal a.\is. 

 = 1554 X 106 at 45° to the principal axis. 



Mica 



(E„ 



In the IIkxaoonal System, Voigt gives measurements on a beryl crystal (emerald). 



The subscripts indicate inclination in degrees of the axis of stress to the principal axis of 



the crystal. 



£0 = 2165X106, E.J5 = 1796 X 106, E9o = 23i2X 106, 



To^667 X lo*'', P9o= 883X106. The smallest cross dimension of the 



prism experimented on (see Table 82), was in the principal axis for this last case. 



In the RH(jMHOHEr)Ric Sy.stem, Voigt has measured quartz. The subscripts have the 

 same meaning as in the hexagonal system. 



Eo= 1030X106, E_ 45= 1305 X 106, E+45 = 85oX 106, £90= 785X106, 



To = 508 X 1 06, T90 = 348 X 106. 

 Baumgarten 1[ gives for calcspar 



Eo= 501X10", E_45 = 44i X106, £ + 45 = 772X106, £90 = 790X106. 



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

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

 third and equally inclined to all three axes respectively. 



t Voigt, " Wied. Ann."' vol. 31, 34— ^5. 



t Koch, "Wied. Ann." vol. 18. 



§ Heckenkamp, "Zeit. fiir Kryst." vol. 10. 



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

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



H Baumgarten, " Pogg. Ann." vol. 152. 



Smithsonian Tables. 



78 



I 



