Page:Collected Physical Papers.djvu/199

Rh It will thus be seen how accurately the indications of the Ag′ receiver measure the intensity of radiation. Further progress in the study of different phenomena connected with electric radiation has been seriously hampered owing to the want of means for measurement of intensity of electric radiation. But this difficulty, as will be seen from the above, is not insuperable.

The strict proportionality of molecular effect can be taken as true only through a limited range. From the results of various experiments, into the detail of which I can not at present enter, it appears that, generally speaking, the curve of response (with molecular effects as ordinates, and the intensities of stimulus as abscissa) is not a straight line. It is at first slightly convex, then straight, and in the last part concave. It is only in the second part that the curve is approximately straight.

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

The state of balance between the effect induced by radiation and the force of restitution on the one hand, and the different equilibrium positions with different radiation intensities on the other, point to the phenomenon being due to molecular strain produced by radiation.