TABLE 46. 

 ELASTICITY OF CRYSTALS. 



75 



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. 



(a) ISOMETRIC SYSTEM.* 



Substance. 



Authority. 



Fluorspar . 

 Pyrite . . 

 Rock salt . 



Sylvine 



Sodium chlorate 

 Potassium alum . 

 Chromium alum 

 Iron alum . 



1473 X io 6 

 3530 X io 6 

 419 X io 6 

 403 X io 6 

 401 X io 6 

 372 X io 6 

 405 X io 6 

 181 X io 6 

 161 X io 6 

 186 X io 6 



1008 X io 6 

 2530 X io 6 

 349 X io 6 

 339 X io 6 

 209 X io 6 

 196 X io 6 

 319 X io 6 

 199 X io 6 

 177 X io 6 



910 X io 6 

 2310 X io 6 



303 X IO 6 



345 X io 6 



1075 X io 6 



I29X io 6 



655 X io 6 



Voigt.f 



Koch.J 

 



Voigt. 

 Koch. 

 Beckenkamp. 



(6) ORTHORHOMBIC SYSTEM.] 



Substance. 



Barite 

 Topaz 



620 X io 6 



2304 X io 6 



E 2 



Xio 6 



959 X io 6 

 2652 X io 6 



376 X io 6 

 2670 X io 6 



702 X io 6 

 2893 X io 6 



740 X io 6 

 3180 X io 6 



Authority. 



Voigt. 



Substance. 



Authority. 



Barite 

 Topaz 



283 X io 6 

 m6x io 6 



293 X io 6 

 1353X10' 



121 X IO 6 



1104 X io 6 



Voigt. 



In the MONOCLINIC SYSTEM, Coromilas (Zeit. fur Kryst. vol. i) gives 

 Gvpsum f E ^ = 88 7 X io 6 at 21.9 to the principal axis. 

 I E^u^ 313 Xio 6 at 75.4 " " " 



Mica | Emax = 2213 X Io6 in the P rinci P al axis - 



E min = 1554 X io 6 at 45 to the principal axis. 



In the HEXAGONAL 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. 



E =2i65Xio, 45=1796 Xio 6 , E 90 =231 2 Xio 6 , 



TO = 667 X io 6 , Tgo = 883 X io 6 . The smallest cross dimension of the 



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



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

 same meaning as in the hexagonal system. 



0=1030 Xio 6 , E_ 45 =1305 Xio 6 , +45 = 850 Xio 6 , 90=785X108, 



To = 508 X io 8 , T 90 = 348 X io 6 . 

 Baumgarten H" gives for calcite 



= 501 X io 6 , E_ 45 = 441 X io 6 , + 45 = 772 X io 6 , E 9 o = 79 X io 6 . 



* 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. 



T Voigt, " Wied. Ann." 31, p. 474, p. 701, 1*87 ; 34, P- 981, 1888; 36, p. 642, 1888. 



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



Beckenkamp, "Zeit. fur Kryst." vol. io. 



|| 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. 



IT Baumgarten, " Pogg. Ann." 152, p. 369, 1879. 

 SMITHSONIAN TABLES. 



