ABSTRACT
One of the chief differences between light and cathode rays lies in their power to pass through solid bodies. The very substances which are most transparent to all kinds of light offer, even in the thinnest layers that can be made, an insuperable resistance to the passage of cathode rays. Metallic layers of moderate thickness are of course as opaque to cathode rays as they are to light. As long as the vacuum is only moderate, the cathode rays fill the whole of the discharge tube as a powerful cone of light, and the glass only phosphoresces outside the patch covered with gold. The metallic layer has a reflecting surface by which the phosphorescent light is reflected. This reflecting surface prevents the light from radiating toward the cathode, but it doubles the intensity of the light in the direction away from the cathode.
