Elasticity of Ferromagnetic Substances by Magnetization. 79 



calculate the change of the ratio from the changes of 

 elasticity and rigidity for the same tension. 

 If <r be the Poisson ratio, we have 



K 



/5E_3K^ 

 l K K /* 



E 



The value of ^= used in the calculation of the following 



K 



BE 



SK 



table is that for no field ; and the values of -^r and -^- 



are those obtained by the tension effect of the magnetic 

 elongation and by Barus's method respectively, for in these 

 two sets of experiments, the stress was first applied and then 

 the magnetizing field. 



Table XXXV. 



Specimen... 



Nickel. 



Swedish 

 Iron. 



Tungsten i 



Steel. 



28-74 %Ni. 50-72 %NL 



70-32% ML 



Tension... 



3020 gr. 



3270 gr. 



3320 gr. j 



1770 gr. 3350 gr. 



3280 gr. 



H. 



C(T ., na 



— X 10-. 

 a 



— xio-. 



Off n „, 



— x 10 2 . 



a 



8<r ._. Su ,_. 

 — X 10-. — x 10-. 

 a <r 



cV xioi 



10 





- 22 





- 0-3 



- 1-6 



20 





- 3-8 





-10 







30 



- 6-1 





00 





- 1-9 





100 



+ 37 



- 74 



00 



-1-3 - 8-3 



-n-5 



150 



+50 











200 



+23 



- 90 



o-i 



-1-3 



-10-1 



— 135 



250 



+ 7 













300 







03 



-11 





-13-8 



350 





-102 







-111 





From the above table, it will be seen that the Poisson ratio 

 is generally diminished by magnetization. In nickel, it is 

 very large, amounting to even 50 per cent. ; but in tungsten- 

 steel it is almost zero, indicating a tendency to increase. 

 The change of the Poisson ratio also varies considerably with 

 tension, and the above table shows only an example of the 

 change. 



