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POPULAR SCIENCE MONTHLY. 



latter of whom obtained photographic images 

 quite similar to those of Prof. Rontgen. 

 The rays with which the latter works, and 

 which he calls the X rays, are chiefly seated 

 at the place of most brilliant phosphores- 

 cence 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. Rontgen says, differ from 

 the cathode rays in two important particu- 

 lars. 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 alu- 

 minum images were obtained on a photo- 

 graphic plate which point to a possible 

 deviation. Lenses apparently have no effect 

 in concentrating the X rays. The transpar- 

 ency 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 per- 

 meability, 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 phenom- 

 ena 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 re- 

 fraction : " 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 every- 

 thing and in which the molecules of bodies 



are imbedded. ... It is known that Le- 

 nard, 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. 

 Rontgen closes his paper with the following 

 paragraphs: "A kind of relationship be- 

 tween 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 longi- 

 tudinal vibrations should exist in the ether, 

 and according to the view of some physicists 

 must exist. It is granted that their exist- 

 ence has not yet been made clear, and their 

 properties are not experimentally demon- 

 strated. Should not the new rays be ascribed 

 to longitudinal rays in the ether? I must 

 confess that I have in the course of this re- 

 search made myself more and more familiar 

 with this thought, and venture to put the 

 opinion 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 beau- 

 tifully the bones and joints. 



The Incubator Bird (Megapodius Tu- 

 muli). 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 ap- 

 parently 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 disen- 



