462 Trof. J. C. Bose. On Electric Touch and tlie Molecular 



j Sign of electric toucli. 



1 

 1 



Action of radiation on the 

 fresli or A variety of 

 tlie snl3stance. 



Further aotion of radiation 

 on the radiation 

 product or B variety. 



i Negative, e.g., arsenic, . . 



i 



Diminution of resistance. 

 Increase of resistance. 



Increase of resistance. 

 Diminution of resistance. 



We haA'e thus two distinct classes of phenomena dependent on the 

 sign of electric touch. If Kj^ represents the conductivity of the fresh 

 substance, and Kg the conductivity of the radiation product, then 



(1) With positive substances, as the conductivity of the radiation 

 product is greater (Kb>IvOj the first action of radiation would be to 

 produce a diminution of resistance. This diminution will continue to 

 be exhibited till the maximum amoiuit of B variety is produced. The 

 fiu'ther action of radiation now will be to reconvert B into A ; but as 

 K^< Kb there would now be produced a diminution of conductivity, 

 and a galvanometer in circuit ^ill indicate an electrical reversal. The 

 reconverted A variety may again be transformed to a greater or less 

 extent to B, and in this way a series of reversals may take place, due 

 to the continued action of radiation producing oscillation in molecular 

 or atomic groupings. I shall designate this as the phenomenon of 

 radio- molecular oscillation. 



(2) With negative substances the conductivity of the radiation pro- 

 duct is less (K < Ka), and the first action of radiation will therefore be 

 an increase of resistance. The phenomena exhibited by these negative 

 substances will precisely be opposite to those shown by the positive 

 substances. 



The above is but an approximate representation of the phenomena. 

 To be more accurate, one has to take into account the partial changes 

 and the eff'ect of radiation on these changed products. Thus, at first 

 suppose the suljstance to be entireh^ made up of A variety (this would 

 rarely be the case). The first flash of radiation converts a large por- 

 tion of A into B, the substance now being a mixture of A and B. The 

 action of the next flash would be to convert the unchanged A into B, 

 and reconvert to a more or less extent B into A. The electric response 

 will thus be very strong at the beginning, but will become con- 

 tinuously less and less. Allien the proportion of B has attained a 

 maximum value, the reconversion of B into A will become relatively 

 large, and thus give rise to reversal effect. 



I spoke of the conversion "to a greater or less extent " of one 

 variety into the other. There is also the question of the relative 

 stability of the two varieties under the given conditions. From the 

 above it will be seen what possibilities there are in the way of difi"erent 

 combinations, and the varied phenomena thereby rendered possible. I 

 will presently describe some of the typical cases. 



