160 



Prof. J. C. Bose. On the Continuity of [Apr. 18, 



the stimulus is strong. The difference exhibited by various substances 

 as regards self-recovery is one merely of degree. I give below typical 

 cases which exhibit the gradual transition from so-called non-recovery 

 to complete recovery. 



The galvanometer used is a dead-beat D'Arsonval, in which the 

 period taken for the maximum excursion and the return to zero from 

 that position is less than half a second. 



In these experiments the receiver was appropriately fixed on a heavy 

 base. This rested in turn on a steady pedestal with one or two sets 

 of pneumatic tyres interposed. 



Positive Type. — In fig. 2 (a) is shown the effect of radiation on Fe 3 4 

 when cold. Only the upper portion of the curve is given ; the flash 

 of radiation produced a deflection of the galvanometer of sixty-four 















(b) 







(C) 













































V 





\ 



































































































































60" 









60" 







3 







Time. 



Fig. 2. — Different stages in the evolution of a Molecular Receiver from a non- 

 recovering to a self-recovering condition. The substance used is Fe 3 4 , 

 representing positive type, which, exhibits a diminution of resistance under 

 electric radiation, (a) the so-called non-recovery, really a case of very slow 

 recovery ; (b) the same slightly warmed, exhibiting a partial and arrested 

 recovery ; (c) the same with increased molecular mobility, recovery in 30". 

 In this and tlie following cases, thick lines represent tlie effect of radiation, 

 thin lines represent the recovery. 



divisions. It will be observed that it had recovered to the extent of 

 three divisions in the course of 60 seconds ; if the rate of recovery had 

 been uniform, there would have been complete recovery in about 

 21 minutes ; but in the later stages, as we shall see, recovery is rather 

 slow. In (b) is shown the effect of increased molecular mobility due to 

 cautious warming. Now there was semi-recovery in 60 seconds • the 

 quickness of recovery went on improving, and after a while the 

 recovery was completed in 30 seconds. 



