Page:On the Continuity of Effect of Light and Electric Radiation on Matter.djvu/9

162 5. A Self-recovering and Metrical Receiver.

But the most perfect type of self-recovering receiver that I have succeeded in constructing was made of the strained variety of silver described in my previous paper. I there showed that this variety of silver exhibits, under the action of radiation, an increase of resistance. I had with me a portion of this variety prepared more than a year ago, and it is probable that time had improved its quality. I made with it a receiver by having about 3 mm. thickness of the powder between two electrodes, one of which, by means of a micrometer screw, could be made to produce a gradual compression. The applied electromotive force was 0·4 volt, and the resistance of the receiver was equal to 20 ohms. The receiver showed the usual increase of resistance at first, with a tendency to self-recovery. In about half an hour it began to exhibit the most perfect self-recovery, and for the next 3 hours of continuous work it went on giving an extraordinary consistency of response.

A short rod was the source of radiation throughout these experiments. The intensity of incident radiation was varied by changing the distance of the radiator. In fig. 4 are given responses to individual flashes at distances of 40 and 15 cm. It will be seen that the

effects are very consistent, the occasional variation being probably due to certain oscillatory sparks not having been as efficient as the others.

Certain Analogies with the Phenomenon of Phosphorescence and