472 Prof. J. C. Bose. On Electric Touch and. the Molecular 



ance in both the classes of fatigued substance), but by removing the 

 strain in B and thus converting it into A. 



The effect of electric radiation is thus to produce rearrangement of 

 atoms and molecules in a substance ; so does light produce new 

 atomic and molecular aggregation in a photographic plate — a subject 

 to be dealt with in detail in a future paper. Some of my audience at 

 the Royal Institution (January, 1897) may remember my attempt at 

 explaining the action of the so-called coherers (which, perhaps, may be 

 better described as " molecular receivers ") by analogy with the photo- 

 graphic action. I had then no proofs for the assertion. I have since 

 been able to obtain experimental evidence that the two phenomena are 



Time of Exposure. 



Fig. 9. — Curve showing the Effect of Heat and Mechanical Vibration on a 

 Fatigued Arsenic Receiver. 



h Effect of heat. b' Effect of tapping. 



identical. The coherer may therefore be regarded as a linear photo- 

 graphic plate; since we are more likely to understand the complex 

 photographic action from the consideration of the much simpler action 

 of electric radiation on elementary substances, where the effects are not 

 complicated by secondary reactions, a photographic plate, may be 

 regarded as merely an assemblage of " molecular receivers." I hope 

 also to prove that nearly all the detectors of radiation are molecular 

 receivers in reality. The investigation of this aspect of the subject 

 has given me some extraordinary results ; they seem to connect 

 together many phenomena which at first sight do not seem to have 

 anything in common. Another interesting question, the consideration 

 of which has for the present to be postponed, is, Why is it that the 

 sensitiveness is so marked in discontinuous metallic particles 1 In 

 other words, Why is the phenomenon mainly one of skin or touch 1 Is 

 the phenomenon wholly unknown in continuous solids ? 

 The experiments described in the present paper show : — - 



