Page:"N" Rays (Garcin).djvu/44

22 instead of a very small, brilliant point, a luminous patch of about 2 cms. diameter, of much less luminosity, whose variations can be far better appreciated by the eye.

The action of an incandescent body on a flame, or that of a flame on another flame, is certainly a common phenomenon. If it has remained unnoticed up to the present, it is because the light of the source prevented the observation of the variations in glow of the receiving flame.

Quite recently I observed another effect of the "N" rays. It is true that these rays are unable to excite phosphorescence in bodies which can acquire this property under the action of light, but when such a body—calcium sulphide, for instance—has previously been rendered phosphorescent by exposure to sunlight, if it is then exposed to "N" rays—for instance, to one of the foci produced by a quartz lens—the phosphorescent glow is observed to increase in a very marked fashion; neither the production nor the cessation of this effect appear to be absolutely instantaneous. Of all the actions producing "N" rays, this is the one which is