RESEARCHES ox MAGNETOSTRICTION. 



:;s;i 



Table. 1 



dl 



i 



- 2.5 x 10- 



- 7.5 



- 20.5 



- 33.8 



- 50.0 



- 65.0 

 -124.0 

 -158.0 

 -175.G 

 -201.3 

 —214.1 

 -217.6x10" 



■0.01 x 

 ■0.03 

 ■0.07 

 ■0.13 

 ■0.22 

 •0.34 

 ■ 1 .00 

 •1.59 

 ■2.04 

 2.47 

 ■2.70 

 •2. SM 



10-' 



fc'(calc) 



14930 



11410 



7800 



5700 



4740 



3930 



L850 



1040 



650 



330 



200 



130 



ft" (cale! 



+ 46400 

 + 35760 

 + 24710 

 + 18150 



+ 1501(1 

 + 12470 



5910 



3340 



2(100 



loco 



630 



410 



sä' + k 



+ 1610 

 + 1530 

 + 1310 

 + 1050 

 + 820 

 + oso 

 + 360 

 + 220 



+ 140 



+ 70 



+ 30 



+ 20 



The value of o/.' + ft" given in the last column were calculated 

 from the change of volume alone. The coefficients k' and k" are very 

 large in low fields and diminish rapidly as the field is increased. The 

 values of ;>// + /,;'' calculated from the strains caused by magnetization 

 show that it is generally very small, satisfying the condition 



3k' 



Since the change of magnetization due to increase of volume a is 



ùl — — \lt-\ — : — Y , we see that if I' -\ — —^>0, there must he increase 

 of magnetization by compression. 



Thus, if we accept Ivirchhoffs theory, smallness of the volume 

 change by magnetization is necessarily accompanied by the smallness 

 of the effect of hydrostatic pressure, as already verified by experiment ; 

 and the strains produced by magnetization in nickel show that the 

 compression must tend to increase the magnetization. 



Using the experimental results for the changes of magnetization 

 by longitudinal pulls, 0.19 kg. sq. mm. and 0.38 kg. sq. mm., 



