170 



Prof. J. 0. Bose. On the Continuity of [Apr. 18, 



I give below the results of three other experiments with different 

 •combinations : — 



Original New value after the Percentage 



E.M.F. action of radiation reduction. 



I , 1-26 V. 1-15 V. 9 



II 0-39 Y. 0-312 V. 20 



III 0-065 Y. 0-039 V. 40 



I was now desirous of obtaining a continuous record of electro- 

 motive changes produced by the continued action of electric radiation. 

 For this purpose I used a galvanometer. 



A cell was made, in the way previously described, with magnesium 

 powder. Owing to some differences in the two portions of the powder 

 there was an initial P.D. of 0*042 V. between the two electrodes. I 

 now had the cell balanced by the potentiometer method, a sensitive 

 galvanometer (with an interposed high resistance) being used as the 

 detector of electric variation. Fig. 8 (a) shows the deviation from 

 the balanced position by radiation which nearly reduced the potential 

 difference to half its original value. By tapping, the original P.D. 

 was restored, and a second experiment (see (b) ) gave almost identical 

 results. 



<3 * 



Position x 

 ofbaiance. 







(CL) 











(b) 



































■ 



















t 



























Time of Eccposure 



Fig. 8. — E.M. variation in a Mg receiver. The original E.M.F. was 0'042 Y. This 

 was reduced to 0'021 Y. by electric radiation. 



It is thus seen that the curve of electromotive variation due to 

 radiation is similar to that obtained by the conductivity variation 

 method. 



It has already been shown that when the range of electric elasticity 

 of the substance is not narrow, or when the strain is not too great, 

 there is a recovery. That on subjecting the substance to the con- 

 tinued action of radiation there is a limiting effect ; that too long con- 

 tinued action tends to produce an electric reversal ; that too feeble an 

 intensity may also produce a reversed effect. We shall now study 

 whether visible radiation produces similar effects. 



