133. X-RAYS APPARENTLY PASSED AROUND A CORNER. Referring to the figure “X-ray Diffusion Fig. 1”, p. 129, it will be noticed that there were three principal elements. First a discharge tube, then a thick steel plate and then a sciascope, all arranged in the proportion indicated in the figure, where the sciascope was within six inches of the edge of the plate, “well within the shadow” thereof. § 69. Fluorescence was seen under these conditions. When the sciascope was directly behind the middle of the plate and opposite the discharge tube, there was no fluorescence, showing that the plate was thick enough to cut off all the rays and therefore the energy must have traveled in two directions for some reason or other. Prof. Elihu Thomson remarked concerning this experiment that he considered, in view of some experiments of his own, on diffusion and opalescence (§ 103), that the sciascope was luminous in view of reflection (§ 146) of the X-rays from various objects in the room, as from the walls and floor of the room, tables, metal objects, electrical apparatus and so on. Theory admits the property of diffraction, which would cause the rays to turn around the edge of the plate, according to the principles of diffraction of light, provided the X-rays were due to transverse or longitudinal or any vibrations. See _Elect. Eng._, N.Y., April 15, p. 378. While Edison generally devotes his energy to actual experiments and dealings with facts and principles, rather than with theories, yet, in this instance, he merely suggested that the fluorescence under the conditions named might indicate that the propagation of X-rays was similar to that of sound in air, the wave being of exceedingly short length. He referred to Le Conte’s experiment of ’82 (see _Phil. Mag._, Feb. ’82), where an experiment of a somewhat similar nature was performed in connection with the propagation of sound. [Illustration: X-RAY DIFFUSION, FIG. 1, § 133. ]