24 T. MIZUNO. 



discharges in the primary spark-gap are oscillatory, the) have an 

 effect on the grating, but if not oscillatory, none. 



II. Inasmuch as where my rectilinear tinfoil resonator fails the 

 tinfoil grating shows the presence of electric waves, the latter must be 

 regarded as far more efficient than the former as a detector of electric 

 waves. Even a single spark, if oscillatory, is sufficient to produce a 

 large effect on the grating. I would here call attention to the fact 

 that the change in resistance of one and the same grating observed on 

 different days during the course of my research differed in amount. 

 This is certainly due to the conditions of the spark-gap, and conse- 

 quently the intensity of the primary oscillations, and also somewhat 

 to the time of exposure. 



III. The sensibility of gratings may, up to certain limits, be 

 increased by increasing the fineness and closeness of the strips. For, 

 of my two gratings which are nearly equal in their dimensions but 

 greatly different in the number of strips, the first gave the maximum 

 change of about () °/o 3 while the second gave about 19 °/ . 



IV. The phenomenon under consideration may not be molecu- 

 lar, and so far as my experiments go, seems to be purely mechanical. 

 Slits cut in tinfoil with a knife, however sharp they may be, surely 

 have margins which are zigzag. I imagine that the action of electric 

 waves may consist in giving impulses to several strips of tinfoil so as 

 to let the leaflets on the margins come in contact with one another 

 and thus cause a diminution of the total resistance of the grating. 

 Especially the fact that the spacing of the strips should have so 

 large an influence as to reduce the effect almost to nothing seems to 

 me to favour the above supposition. Also the fact that the change 

 of resistance depends upon the orientation of the strips seems to point 

 in the same direction. Still another fact which is equally important 

 from the above point of view is that the resistance of the tinfoil 



