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Their common origin in the emission of an Auer burner is favourable to such a view, as is also the opacity of rock-salt and of water. But on the other hand, for Auer rays, the transparency of metals and other substances opaque to Rubens rays constitute an apparently radical difference between the two sorts of radiations (note 7).

On New Sources of Radiations capable of

traversing Metals, Wood, etc., and on New Actions produced by these Radiations (May 25, 1903).

While investigating whether radiations analogous to those whose existence I recorded in the emission from an Auer burner (see p. 13) are not to be met also in other sources of light and heat, I established the following facts : the flame of an annular gas-burner emits such radiations; the chimney, however, should be removed, on account of the absorption of the rays by glass. A Bunsen burner scarcely

produces any. A piece of sheet-iron or silver, heated to dull redness by a Bunsen burner, placed behind them, gives off rays at about the same rate as an Auer burner.

A plate of polished silver was arranged so that its plane made an angle of 45° with the horizontal plane. This plate having been heated to cherry-red by a Bunsen burner, its upper face emitted rays analogous to those of an Auer burner. A horizontal pencil of these rays, after traversing two sheets of aluminium of 0-3 mm. total thickness, sheets of black paper, etc., was concentrated by a quartz lens ; with the aid of the small spark, the existence of four focal regions was ascertained. I further found that the action on the spark was much more pronounced when the spark was arranged vertically—that is, in the plane of emission—than when it was normal to this plane. The new radiations emitted by the polished plate are therefore polarized, as are the light and heat emitted at the same time. The silver plate having been covered with lampblack, the intensity of emission increased, but the polarization disappeared.

The foregoing leads one to think that the emission of radiations susceptible of traversing metals, etc., is an extremely general phenomenon. First observed in the emission of a focus tube, it was also met in that of ordinary sources of light and heat. For shortness, I will henceforward designate these rays by the name of “N” rays.

I would draw attention to the fact that these “N” rays comprise a very large variety of radiations ; for while those which issue from an Auer burner have refractive indices greater than 2, there are others, amongst those emitted by a Crookes' tube, whose index is inferior to 1:52, for if a pencil of these rays is made to impinge on an equilateral quartz prism, parallel to the edges and normal to one of the faces, an emerging pencil is obtained which is very much spread out.

Up to this time the only means of detecting the presence of “N” rays was by their

? From the name of the town of Nancy, these researches having been made at the Nancy University. In conformity with a usage which has become established, I now employ the letter "N" instead of “n," which I had at first adopted.

action on a small spark. I asked myself if the spark should in this case be considered as an electric phenomenon, or only as producing incandescence like a small gaseous mass. If this latter supposition were correct, the spark could be replaced by a flame. I then produced a quite small flame of gas at the extremity of a metal tube having a very small orifice. This flame was entirely blue. I ascertained that the flame could be used to reveal the presence of “N” rays just like the spark; for when it receives these rays, it becomes whiter and brighter in just the same way. Its variations in glow allowed of four foci being found in a pencil which had passed through a quartz lens; these foci are the same as those detected with the small spark. The small flame behaves therefore, in regard to “N” rays, just like the spark, save that it does not allow of the observation of polarization phenomena.

In order to study more easily the variations in glow, whether of flame or spark, I examine them through a plate of ground glass, about 25 or 30 mms. distant. In this way one obtains, 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

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