114 



T. MIZUNO. 



electric waves as will be seen from the experiments which I now 

 describe. 



Experiment 1 : A Hertzian parabolic vibrator, ABC, was placed 

 horizontally with aparture turned upwards, as shown in Fin-. IV. 

 The aperture was covered with a 

 sufficiently large wooden plate, ADC, 

 entirely coated with tinfoil. A grating, 

 whose initial resistance was about 71 

 ohms, was placed at about ocm. from the 

 plate and in a vertical line with the 

 primary conductor, 0, radiating electric waves of 60 cm. wave-length. 

 Then, exciting the primary oscillations, I always found that the 

 resistance of the grating was diminished by from 1 to nearly 2 ohms. 



The experiment was repeated after raising the plate, ADC, parallel 

 to itself and keeping it at some height from the aperture, AC. 

 Similar changes of resistance were also observed in this case. This 

 phenomenon may of course be understood by considering the fact 

 that some electric waves, which pass out of the uncovered portions 

 of the parabolic vibrator, will, after going through the room and 

 being reflected from the surrounding walls, ceilings, &c, come back 

 ultimately to the grating in a much enfeebled state. 



Experi'iicnt 2: The above experi- 

 ment was modified by placing on the 

 plate, A D C, a zinc box, abed, 17 cm. 

 by 27 cm., without top or bottom and 

 putting the grating inside it. In this 

 case also, a change of resistance, was 

 observed though smaller. It is then certain that although the side 

 effects were got rid of, the top effect still remained, through which 

 traces of waves might affect the resistance of the gratinrr. The 



