16 



T. MIZUXO. 



by a spark-gap, and it« ends furnished with brass spheres 4 cm. 

 in diameter forming the poJes. Ihe wave-length of the electric waves 

 produced was ascertained to be about 60 cm. The vibrator was placed 

 in the focal line of a wooden parabolic cylinder coated inside with 

 tinfoil, whose height was 76 cm., depth 21 cm., and focal length 

 12 cm. My resonator is very simple in construction and has been 

 found very convenient in my other researches on electric waves. It 

 is merely a rectangular strip of tinfoil, OS cm. in breadth and 60 

 (30 in some case) cm. in length, with a gap in the middle, which is 

 so fine that resonance-sparks can easily pass across. 



4. I will now describe some experiments (Ex. 1 Ex. 6) with 



the view of showing to what extent metallic gratings can screen the 

 action of electric waves. 



Experiment 1. 



A wooden board, on which were pasted two parallel tinfoil strips. 

 33 cm. in length and at a distance of 9.7 cm. from one another, was 

 set up vertically in front of the parabolic cylinder at a. distance of 

 about 30 cm. from the vibrator. The grating No. 1 was brought 

 behind the board, and after exposure for about half a minute to electric 

 waves, its resistance was examined by a Wheatstone's bridge. The 

 results obtained were as follows : — 



As Herr Aschkinass mentions, the resistance of the grating once 

 diminished by the action of electric waves could be restored almost 



