The Effect of Stress on Magnetization. 65 



the series of holes (considered as a grating) is in the act o£ 

 passing off, and it is evident that the peculiar interference 

 is due to this circumstance *. The argument applies even 

 more strongly, if less simply, to an actual grating formed by 

 a series of narrow parallel and equidistant slits cut in an 

 infinite screen. 



The case of a reflecting grating differs in some important 

 respects from that above considered. An investigation appli- 

 cable to light is now nearly completed. It confirms the 

 general conclusion that peculiarities are to be looked for at 

 such angles of incidence that spectra of higher order are just 

 passing off, but (it is especially to be noted) only when the 

 polarization is such that the electric vector is perpendicular 

 to the grating. 



Tei-ling Place, Witham, May 4. 



P.S. June 5. — In answer to farther inquiry Prof. Wood 

 tells me that he thinks the ruling may perhaps be 15020 to 

 the inch, but (the grating being for the time out of his hands) 

 he is not able to speak with certainty. 



IV. On the Effect of Stress on Magnetization and its 

 Reciprocal Relations to the Change of Elastic Constants by 

 Magnetization. By K. Honda and T. Terada, Lecturers 

 on Rhysics in the Tokyo Imperial University f. 



[Plates I-V.] 



IX our previous experiments, we investigated in some 

 detail the change of elastic constants of several ferro- 

 magnetic metals and alloys caused by magnetization, with 

 special regard to the order of applying the stress and the 

 field, and found that in some cases the change is considerably 

 large, and moreover that it differs more or less for different 

 orders of applying the stress and the field. In order to find 

 the proper explanation of these facts, it will be necessary to 

 investigate with the same specimens as in the previous 

 experiment the change of magnetization by stress, with 



* If e be not a precise multiple of \, the series l + i+-g-+ .... 

 ad infin. would "be replaced by 



wliich is equivalent to 



—log {2 sin (pe)} +| i (ke—n). 

 t From the Journ. Coll. Sci. Tokyo. Communicated by the Authors. 

 Phil, Mag. S. 6. Vol. II. No/?9. July 1907, F 



