Page:Collected Physical Papers.djvu/164

144 The following tabulated statement indicates the phenomena exhibited by two classes of substances:—

We have thus two distinct classes of phenomena dependent on the sign of electric touch. If K$A$ represents the conductivity of the fresh substance, and K$B$ the conductivity of the radiation product, then—

(1) With positive substances, as the conductivity of the radiation product is greater (K$B$ > K$A$), the first action of radiation would be to produce a diminution of resistance. This diminution will continue to be exhibited till the maximum amount of B variety is produced. The further action of radiation now will be to reconvert B into A; but as K$A$ < K$B$ there would now be produced a diminution of conductivity, and a galvanometer in circuit will 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