"N" Rays/On New Actions Produced by "N" Rays; Generalization of Phenomena Already Observed
On New Actions produced by "N" rays—Generalization of the Phenomena already observed (November 2, 1903).
When a pencil of "N" rays is directed either on a small spark, flame, or a phosphorescent substance previously exposed to the sun's rays, or, again, to a platinum plate heated to dull redness, the light emitted by these various sources is seen to increase in glow. In these experiments, one operates on sources emitting light spontaneously. I asked myself whether one could not generalize these experiments by using a body not emitting light itself, but reflecting that which reaches it from an external source. I consequently carried out the following experiment: a slip of white paper, 15 mms. long and 2 mms. broad, is fixed vertically to a wire holder; the room being made dark, the slip is dimly lighted by projecting laterally on it a pencil of light, emitted by a small flame shut up in a box, in which a vertical slit is pierced.
On the other hand, the rays are produced by the following contrivance: an Auer burner, provided with a sheet-iron chimney, in which a rectangular orifice, 60 mms. high and 25 mms. broad, has been cut, is enclosed in an iron lantern pierced with an opening placed in front of the chimney orifice, and stopped up by a plate of aluminium. In front of this window the small slip of paper is placed, illuminated in the manner indicated above. If, now, the rays are intercepted by interposing a sheet of lead or the hand, the small paper rectangle is seen to darken, and its contours to lose their sharpness; the light diffused by the slip of paper is thus increased by the action of "N" rays.
The following idea then presented itself: the diffusion of light is a complex phenomenon, in which the elementary fact is regular reflection, and consequently there is reason for ascertaining experimentally whether the reflection of light is, or is not, modified by the action of "N" rays. For this purpose, a polished steel knitting-needle was fixed vertically in place of the slip of paper of the former experiment; at the same time, in a box completely closed, with the exception of a vertical slit cut at the same height as the Auer burner, and stopped up by transparent paper, a flame was disposed so as to light up the slit. By suitably placing the eye and the slit, the image of this latter is seen formed by reflection on the steel cylinder, and simultaneously the reflecting surface is receiving the "N" rays. It was then easy to observe that the action of these rays reinforces the image, for if they are intercepted, the image darkens, and turns to a reddish hue. I repeated this experiment with the same success by employing, instead of the knitting-needle, a plane mirror of bronze.
The same result is again obtained by reflecting the light on the polished face of a block of quartz. However, when the "N" rays fall normally on the refracting face, their action on reflected light disappears, whatever be the incidence of this light, whether it be that their action becomes zero, or simply inappreciable. In order that the light reflected by the quartz may be reinforced by the "N" rays, it is not necessary that the rays should be directed towards the interior of the quartz; the action still occurs when the "N" rays traverse the reflecting surface from the inside towards the outside.
All these actions of "N" rays on light require an appreciable time-interval for appearing and disappearing. I was unable, although I varied the experiment in a great many ways, to observe any action of "N" rays on the refracted light.
I will here make the following general remark concerning the observation of "N" rays. The aptitude for catching small variations in luminous intensity is very different in different persons; some see from the outset, and without any difficulty, the reinforcing action produced by "N" rays on the brightness of a small luminous source; for others, these phenomena lie almost at the limit of what they are able to discern, and it is only after a certain amount of practice that they succeed in catching them easily, and in observing them with complete certainty. The smallness of the effects and the delicacy of their observation must not deter us from a study which puts us in possession of radiations hitherto unknown. I have recently observed that the Auer burner can be advantageously replaced by the Nernst lamp, without a glass, this lamp giving more intense "N" rays. With a 200-watt lamp, the phenomena are marked enough to be, in my belief, easily visible to any one at the first trial.