Page:Collected Physical Papers.djvu/241

Rh An instance of this is seen in the development of mechanical pressure marks. Images produced by electric strain are observed in the "inductoscripts."

It is thus seen—

(3) That molecular strain may not only be produced by visible or invisible radiation, but also by (a) electric induction, and (b) by mechanical distortion. Latent images produced by such means may be developed, e.g., inductoscripts, and pressure marks.

(4) That nearly all substances are sensitive to radiation, but the effect cannot in all cases be rendered visible, (a) owing to want of suitable chemical developers, (b) owing to quick self-recovery. The molecular effect due to radiation can, however, be demonstrated by the conductivity or electromotive variation methods.