66 



Messrs. K. Honda and T. Teracla on the 



special regard to the order of applying the stress and 

 the field. 



Since J. J. Thomson * gave his theoretical exposition of 

 the reciprocal relations between magnetism and strain, 

 several theories f in the same field have been published, and 

 the present investigation may also afford interesting materials 

 for testing the validity of these theories. In this direction, 

 we have been preceded by Ren sing J and Cantone §, in the 

 case of iron and nickel ; but a more extended research 

 may not be undesirable. With this view, sets of experiments 

 have been undertaken, firstly to investigate the change of 

 magnetization by applying successive stresses under constant 

 fields; and secondly, to investigate the magnetization by 

 applying the magnetizing field under different constant 

 stresses and thence to deduce indirectly the change of 

 magnetization by stresses. 



Specimens used had the following dimensions : — 



Specimens. 



Length. 



Diameter. 



Demagnetizing 

 factor. 



Swedish iron. 



21-30 cm. 



0-903 mm. 



0-00089 



Tungsten steel. 



26-85 



0-885 



0-00050 



Nickel. 



26-87 



0-863 



00056 



28-74 per cent. Mi. 



26-80 



0-964 



0-00063 



50 - 72 per cent. Ni. 



27-00 



0-880 



0-00050 



70-32 per cent. Ni. 



26-86 



0-891 



0-00068 



§ 1. Appaeatus. 



The intensity of magnetization was measured by the 

 ballistic method. This method was preferred to the magneto- 

 metric one, since in our experiments fields up to 400 c.G.s. 

 units were required, and consequently the adjustment of a 

 very sensitive magnetometer placed close to a pair of com- 

 pensating coils traversed by a strong current would be 

 extremely troublesome. The magnetizing coil, which was 



* J. J. Thomson, ' Application of Dynamics to Physics and Chemistry/ 

 Chap. iv. 



t F. Kolacek, Ann. d. Phys. xiii. p. 1 (1904); Ann. d. Phys. xiv. 

 p. 177 (1904). A. Heydweilier, Ann. d. Phys. xi. p. 602 (1903). K. 

 Cans, Ann. d. Phys. xiii. p. 634 (1904). S. iSano, Proc. Tokyo Math.- 

 Phys. Soc. ii. p. 175 and p. 207 (1904). 



X Sensing, Ann. d. Phys. xiv. p. 363 (1904). 



§ Cantone, Rend. d. 1st. Lomb. (2) xxxvii. p. 435 (1904). Ibid. 

 pp. 474, 535 & 567. 



