276 Messrs. H. Nagaoka and K. Honda on Magnetostriction- 

 applied longitudinally, as well as that due to twisting-wrench, 

 is always accompanied by a shearing strain, a result which 

 will be of no small value in the theory of molecular mag- 

 netism. 



Effects of Longitudinal Pull on the Magnetization of Iron and 

 Nickel. — This subject has been studied by several investigators, 

 but, so far as we are aware, the change in magnetization by 

 the application of feeble stress is scarcely known. It will be 

 seen from experiments on the strain produced by magnetiza- 

 tion that the deformation corresponds to the effect of a feeble 

 stress. As our principal object was a comparison of Kirch- 

 hoff's theory of magnetostriction with experiment, we found 

 it necessary to pay special attention to the change in the 

 magnetic qualities of iron and nickel, when the rods of these 

 metals are subjected to small loading, which will strain the 

 ferromagnetic body to an extent comparable with the defor- 

 mation in the magnetizing field. 



As the iron ovoid used in the preceding experiment was 

 unfit for studying the effect of longitudinal pull, an iron rod 

 of 0*273 sq. cm. section made of the same material as the 

 ovoid was used for measuring the change of magnetization in 

 the free and in the feebly stretched condition. The nickel 

 rod used in all the preceding experiments was also examined. 

 The magnetometer was made sensitive by means of the 

 compensation arrangement used in studying the effects of 

 hydros! atic pressure. 



The following table gives the change of magnetization in 

 different fields due to longitudinal stresses 0*19 kg. sq. mm. 

 and 0*38 kg. sq.mm.; corresponding to elongations 0*85 x 10~ 5 

 and 1*71 x 10 ~ 5 resp. in iron ; and to elongations 90 X 10~ 5 

 and 1*8 x 10~ 5 resp. in nickel. 



Iron (fig. 18) . 



Nickel (fig. 19). 



H. 



! 



£1 



dl 



0-38 kg. sq. miii. 



0*19 kg. sq. mm. 



61 



+ 2-15 



4-101 



9-6 



+5-46 



H-2 95 



155 



+ o-74 



+ 3-10 



204 



+ 3-72 



+ 1-85 



27 3 



+2-00 



+064 



346 



+092 



-013 



425 



+0-24 



-0 56 



50-8 



-0-11 



-077 



67-6 



-0-49 



-0-S6 



846 



-069 



-0-94 



H. 



£1 



si 



0*38 kg. sq.mm. 



- 19 kg. sq.mm. ; 



7 9 



+0-63 



+0-52 



14-5 



-696 



-462 



22 2 



-8-35 



-534 



30-2 



-813 



-4-82 



38-5 



-7 07 



-4-16 



47-1 



-5-85 



-373 



55-3 



-502 



-345 



(.3 9 



-441 



-321 



810 



-3-27 



-277 



98-3 



-2-44 



-2-44 



