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T. MIZUNO. 



we find it necessary to give it a greater number of taps to effect this 

 restoration. Later on, when the sensibility has diminished to a 

 certain value, it seems to retain that value without any decided 

 further change for a long time. This variation in the sensibility 

 may be accounted for in the following way. As mentioned in § 5 

 the effective leaflets along the margins of the several tinfoil strips 

 may be of different sizes, and some of them possibly very small. The 

 smaller the leaflets the more sensitive to electric disturbances and 

 consequently the more liable to fatigue will they be. Hence in the 

 primitive state such leaflets are easily affected by even very weak 

 electric impulses, but soon lose this sensibility as a result both of 

 the repeated electric disturbances and of the mechanical taps given to 

 them each time. 



§ 8. Though the sensibility of the grating thus always dimi- 

 nishes to a certain extent by a little use, still it is even in such a state 

 far superior to that of an ordinary Hertzian resonator. Even where 

 the latter fails, the grating always shows the presence of electric waves 

 if there be any. Experiments on the nature of electric waves, 

 namely, on rectilinear propagation, reflection, refraction, diffraction, 

 polarisation, &c, can all be easily carried on by means of a properly 

 constructed grating. Moreover, such a grating gives not only 

 qualitative, but also quantitative results, to a certain extent, because 

 the amount of diminution of the resistance depends upon the quantity 

 of energy of the impinging waves. Hence, I believe, it may prove 

 to be of great advantage to make use of such gratings in all lecture 

 experiments as well as in laboratory researches on electric waves. 



In conclusion I wish to express my thanks to Mr. U. Takashima 

 for the kind and earnest assistance he has given me in the preparation 

 of many of these gratings and in carrying out researches upon them. 



