276 



NA TORE 



[January 23, 1896 



body between the source and a photographic plate or 

 fluorescent screen. 



I have observed and photographed many such shadow 

 pictures. Thus, I have an outline of part of a door 

 covered with lead paint ; the image was produced by 

 placing the discharge-tube on one side of the door, 

 and the sensitive plate on the other. I have also a 

 shadow of the bones of the hand (Fig. i), of a wire 

 wound upon a bolibin, of a set of weights in a box, of a 



Fig. I — Photograph of the bones in the fingers of a living human hand. 

 The third finger has a ring upon it. 



compass card and needle completely enclosed in a metal 

 case (Fig. 2), of a piece of metal where the X-rays show 

 the want of homogeneity, and of other things. 



For the rectilinear propagation of the rays, I have a 

 pin-hole photograph of the discharge apparatus covered 

 with black paper. It is faint but unmistakable. 



(15) I have sought for interference effects of the X-rays, 



-Photograph of a compass card and needle completely 

 enclosed in a metal case. 



of their small 



intensity. 



but possibly, in consequence 

 without result. 



(16) Researches to investigate whether electrostatic 

 forces act on the X-rays are begun but not yet concluded. 



(17) If one asks, what then are these X-rays ; since 

 they are not kathode rays, one might suppose, from their 

 power of exciting fluorescence and chemical action, them 

 to be due to ultra-violet light. In opposition to this view 



NO. 1369, VOL. 53] 



a weighty set of considerations presents itself. If X-rays 

 be indeed ultra-violet light, then that light must possess 

 the following properties. 



{a) It is not refracted in passing from air into water, ; 

 carbon bisulphide, aluminium, rock-salt, glass or zinc. \ 



[b) It is incapable of regular reflection at the surfaces] 

 of the above bodies. 



(<r) It cannot be polarised by any ordinary polarisingj 

 media. 



{d) The absorption by various bodies must depend 

 chiefly on their density. 



That is to say, these ultra-violet rays must behave 

 quite differently from the visible, infra-red, and hitherto 

 known ultra-violet rays. 



These things appear so unlikely that I have sought for 

 another hypothesis. 



A kind of relationship between the new rays and Hght 

 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 demon- 

 strated. Should not the new rays be ascribed to longi- 

 tudinal waves 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 opinion forward, while I am quite 

 conscious that the hypothesis advanced still requires a 

 more solid foundation. 



PROFESSOR RONTGENS DISCOVERY. 

 T^HE newspaper reports of Prof Rontgen's experiments 

 -*■ have, during the past few days, excited considerable 

 interest. The discovery does not appear, however, to 

 be entirely novel, as it was noted by Hertz that metallic 

 films are transparent to the kathode rays from a Crookes 

 or Hittorf tube, and in Lenard's researches, published 

 about two years ago, it is distinctly pointed out that such 

 rays will produce photographic impressions. Indeed, 

 Lenard, employing a tube with an aluminium window, 

 through which the kathode rays passed out with com- 

 parative ease, obtained photographic shadow images 

 almost identical with those of Rontgen, through pieces 

 of cardboard and aluminium interposed between the 

 window and the photographic plate. 



Prof Rontgen has, however, shown that this aluminium 

 window is unnecessary, as some portion of the kathode 

 radiations that are photographically active will pass 

 through the glass walls of the tube. Further, he has 

 extended the results obtained by Lenard in a manner 

 that has impressed the popular imagination, while, 

 perhaps most important of all, he has discovered the 

 exceedingly curious fact that bone is so much less trans- 

 parent to these radiations than flesh and muscle, that if 

 a living human hand be interposed between a Crookes 

 tube and a photographic plate, a shadow photograph can 

 be obtained which shows all the outlines and joints of 

 the bones most distinctly. 



Working upon the lines indicated in the telegrams from 

 Vienna, recently published in the daily papers, I have, with 

 the assistance of Mr. J. C. M. Stanton, repeated many of 

 Prof Rontgen's experiments with entire success. Ac- 

 cording to one of our first experiments, an ordinary 

 gelatinous bromide dry photographic plate was placed in 

 an ordinary camera back. The wooden shutter of the 

 back was kept closed, and upon it were placed miscel- 

 laneous articles such as coins, pieces of wood, carbon, 

 ebonite, vulcanised fibre, aluminium, &c., all being quite 

 opaque to ordinary light. Above was supported a 



