Changes 'produced in Matter hy Electric Waves. 



471 



portion of the curve is a repetition of the curve No. 6, and how the 

 substance arrives at the second fatigued state l' . To observe the 



Time of Exposure 



Fig. 8. — Curve sliowicg the Effect of Heat and Mechanical Yibration on a 

 tatigiied Iron-filings Keceiver. 



* Application of heat. f Application of a tap. 



efJect of mechanical disturbance a gentle tap was given to the receiver, 

 and at once there was produced an increase of resistance due to the 

 transformation of B into A, the receiver regaining its sensitiveness by 

 the transformation. The action of radiation was continued, and after 

 a few reversals the substance once more arrived at the third fatigued 

 state, h". The process described above could be repeated any number 

 of times. 



Effect of Heat and Mechanical Disturbance on a Negative Fcdigued 



Substance. 



Experiments similar to the above were carried out with an arsenic 

 receiver. From the curve given below (fig. 9) it is seen that the 

 reaction of the negative substance is in every respect opposite to that 

 of a positive substance. It will be noticed that the same cause — i.e., 

 heating or tapping — produces, as necessary consequences of the hypo- 

 theses previously stated, two opposite reactions in the two classes of 

 substance. I have been able to verify this deduction by observations 

 with nearly a dozen diflferent substances, and have not, so far, come 

 across anj- to contradict it. It thus appears that tapping restores the 

 sensitiveness not by the separation of the electrically-welded particles 

 (in which case tapping ought to have produced an increase of resist- 



