Jagadish Chandra Bose

“ 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 continued action of radiation there is a limiting effect; that too long continued action tends to produce an electric reversal; that too feeble an intensity may also produce a reversed effect. ”

“ In considering the effect of electric radiation in varying the conductivity of the particles, we have to bear in mind that no explanation can be regarded as complete, unless it explains not only the diminution, but also the increase of resistance; also the phenomenon of automatic recovery and of the opposite effects which are exhibited by the same receiver under different molecular conditions. The increase of resistance of the Ag′ receiver and its instantaneous recovery are directly opposed to the theory of coherence. ”

“ I found that in these cases the sensibility was increased by subjecting the substance to strong radiation or even by passing a few induction shocks. The increase of sensitiveness thus produced appears to be due to the removal of molecular sluggishness. The improvement in sensitiveness often obtained by shaking of the particles is no doubt due to the same cause. In the various types of molecular receivers, whether responding to electric radiation, light, or mechanical vibration, the same effect is noticed. Generally speaking, the receiver in the first place improves gradually with working. ”

“ In the following investigations, the electrical effects, either the conductivity or the electromotive variations, due to external disturbances of various durations, have to be observed. It is also necessary to note the time-relations of the after-recovery from these effects. The conductivity and electromotive variations can be deduced from the observed varying deflections of the galvanometer. When the variations are rapid, the observation requires great alertness and is very fatiguing. ”

“ If the above view is correct then it would be possible to detect the effect of molecular strain due to visible or invisible radiation by the following more or less delicate methods. It is to be borne in mind that the effect of radiation is almost confined to the skin or outer layer of the substance. ”

“ Cautious application of heat often increases, not only the sensibility, but also the power of self-recovery. But excess of temperature produces erratic behaviour by causing violent molecular disturbance. ”

“ Influence of previous History.—As regards the first, I have already shown in my previous paper [2] that a substance strained by radiation often exhibits opposite or reversal effects. Freshly powdered particles often show erratic results, but the effects become consistent after annealing; this often increases the sensibility also, by increasing the molecular mobility. Fresh particles are sometimes found to exhibit very little sensitiveness. ”

“ We thus see the possibility of measuring the molecular change by measuring the correlated variation of any of the properties described above. The choice of a particular method will be governed by special convenience under given conditions. ”

“ 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.
Fig. 8.—E.M. variation in a Mg receiver. The original E.M.F. was 0·042 V. This was reduced to 0·021 V. by electric radiation. ”

“ 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.
Negative Type.—Fig. 3 exhibits the effect on the negative type as exemplified by Sn and Pb coated with Br. It appears that in these, warmth is favourable to quick recovery. For in India with Pb coated with Br the self-recovery was obtained with the greatest ease. Here a more careful adjustment was necessary. At first the flash of radiation produces a sudden increase of resistance, from which there is no immediate
Fig. ”