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144
MOLECULAR CHANGES BY ELECTRIC WAVES
The following tabulated statement indicates the phenomena exhibited by two classes of substances:—
| Sign of electric touch. | Action of radiation on the fresh or A variety of the substance. | Further action of radiation on the radiation product or B variety. |
| Positive, e .g., iron | Diminution of resistance. | Increase of resistance. |
| Negative, e.g., arsenic | Increase of resistance. | Diminution of resistance. |
We have thus two distinct classes of phenomena dependent on the sign of electric touch. If KA represents the conductivity of the fresh substance, and KB the conductivity of the radiation product, then—
(1) With positive substances, as the conductivity of the radiation product is greater (KB > KA), 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 KA < KB 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
