NOTE ON TINFOIL GRATING AS A DETECTOR FOR ELECTRIC WAVES. \ J 



to its original value by tapping it. In this experiment, resonance 

 sparks could be discovered behind the board by means of my tinfoil 

 resonator. 



Experiment 2. 



Next, a third strip was pasted on the board, half way between 

 the other two and the experiment repeated. The results were : — 



Here, the resonance sparks behind the board were very feeble. 



Experiment 3. 



Two more strips were then added bisecting the spaces between 

 those in the experiment 2. 



The resonator behind the board gave no sparks in this case. 



Experiment 4. 



Next, a, grating, rectangular in form, 27 cm. in length and 

 22 cm. in breadth, was made, the average distance between two 

 consecutive strips being about O'O cm. Placing this grating in a 



