Page:Collected Physical Papers.djvu/169

Rh very gradual increase of pressure, effected by means of a fine micrometer screw which moved the compressing electrode in a perfectly parallel manner. There should be no jarring motion, as mechanical disturbance was found to break up the complex atomic aggregation in the radiation product. During eight minutes of exposure the receiver continued to exhibit an increase of resistance, after which the substance became positive, being converted to the B state; this positive state lasted for a minute under exposure to radiation, then there was a reversal to the original negative state, as if the structure so laboriously built up suddenly gave way. Subsequently there were series of reversals, the specimen becoming more and more inert, and, after an exposure of about thirty minutes, the sensitiveness was practically lost.

The curve given below represents approximately the results of the experiment. During certain periods the substance became so nearly neutral that it was difficult to interpret whether the substance was positive or negative. The lower halves of the curve represent the negative and the upper halves the positive states, and the corresponding numbers represent, in minutes, the duration of these states.

It was said that, owing to molecular reversals due to radiation, there should be a corresponding series of