Page:Popular Science Monthly Volume 48.djvu/948

858 latter of whom obtained photographic images quite similar to those of Prof. Röntgen. The rays with which the latter works, and which he calls the X rays, are chiefly seated at the place of most brilliant phosphorescence on the walls of the discharge tube; "that is, the X rays proceed from the front where the cathode rays strike the glass. If one deviates the cathode rays within the tube by means of a magnet, it is seen that the X rays proceed from a new point—i. e., again from the end of the cathode rays." The X rays. Prof. Röntgen says, differ from the cathode rays in two important particulars. Air absorbs the X rays much less than it does the cathode rays; and while the cathode rays are sharply deflected by a magnet, the X rays are apparently not at all affected by a magnet. The X rays could not be deflected by the use of ordinary prisms, but with prisms of ebonite and aluminum images were obtained on a photographic plate which point to a possible deviation. Lenses apparently have no effect in concentrating the X rays. The transparency of a great number of substances to these X rays, such as ebonite, glass, wood, cardboard, platinum, and many others, was tested, as also the effect of the thickness of the substance, and led to the conclusion that the density of the bodies is the property whose variation mainly affects their permeability, but that this alone does not determine the transparency. Increasing thickness increases the hindrance offered to the rays by all bodies. "The justification for the term 'rays' applied to the phenomena lies partly in the regular shadow pictures produced by the interposition of a more or less permeable body between the source and a photographic plate or fluorescent screen." The rays have the property of producing fluorescence in various substances, as barium platino-cyanide, calcium sulphide, uranium glass, Iceland spar, rock salt, etc., as well as of acting on a dry plate. "The retina of the eye is quite insensitive to these rays." Prof. Rontgen says in reference to their refraction: "Since I have found no evidence of refraction at the surface of different media, it seems probable that the X rays move with the same velocity in all bodies, and in a medium which penetrates everything and in which the molecules of bodies are imbedded. . . . It is known that Lenard, in his investigations on cathode rays, has shown that they belong to the ether, and can pass through all bodies. Concerning the X rays, the same may be said." Prof. Röntgen closes his paper with the following paragraphs: "A kind of relationship between the new rays and light rays appears to exist; at least, the formation of shadows, fluorescence, and the production of chemical action point in this direction. Now it has been known for a long time that besides the transverse vibrations which account for the phenomena of light, it is possible that longitudinal vibrations should exist in the ether, and according to the view of some physicists must exist. It is granted that their existence has not yet been made clear, and their properties are not experimentally demonstrated. Should not the new rays be ascribed to longitudinal rays in the ether? I must confess that I have in the course of this research made myself more and more familiar with this thought, and venture to put the opmion forward, while I am quite conscious that the hypothesis advanced still requires a more solid foundation." The most striking of the pictures accompanying the article are the photograph of a compass card and needle completely inclosed in a metal case, and a cut of the human hand showing quite beautifully the bones and joints.

The Incubator Bird (Megapodius Tumuli).—An account in the Geographical Journal of a trip to the little island of Niuafou, in the South Pacific, describes a native bird called the malau, which is apparently of the same order as the Megapodes; it makes no nests, but buries its eggs in the soft, hot sand of this volcanic island. It is about the size of a small domestic fowl. Its eggs are large and of a dull reddish color. The strange nesting habit and the large size of its eggs recall that curious bird the jungle fowl of Australia (Megapodius tumulus). Great numbers of high and large mounds exist in some parts of Australia, which were for a long time thought to be the tombs of departed natives; the natives, however, disclaimed the sepulchral character, saying that they were artificial ovens in which the eggs of the jungle fowl were laid, and which, by the heat that is always