390 Rollins — Cathode Stream and X-Light. 



notes a better one ? This was the theory : When the particles 

 of the cathode stream strike the target, they are heated suffi- 

 ciently to cause them to be radiant centers, from which the 

 short ether waves we call X-light arise. As time is required 

 for heat to decline, the particles are sufficiently hot, when they 

 have rebounded opposite the opening of the passage, to be 

 radiant centers. The wave fronts, therefore, go directly 

 through the passage, to the fluorescent screen, brightly illumi- 

 nating it. I have used the word heat not to distinguish this 

 from electromagnetic phenomena, but to express a more per- 

 sistent state, in the radiant particles of the cathode stream, 

 after they have struck the target, than that represented by the 

 single pulse of the usual theory of X light. I mention an 

 experiment bearing on this heat theory. An X-light tube was 

 made with a hollow target. The area struck by the cathode 

 stream could be cooled to a low temperature. When so cooled 

 there was less X-light. This tube under the title of the 

 A-W-L tube was made commercially, proving capable of con- 

 verting a large amount of electricity into X-light, because with 

 any cathode stream it was impossible to melt the target. I 

 also designed a simpler tube for general use. The target 

 rotated on an axis. Fresh metal could be brought to receive 

 the force of the cathode stream when a hole had been melted. 

 Before closing this paper I shall consider the structure of 

 the atom as seen by the cathode stream and X-light. After 

 Rontgen discovered that some of Lenard's rays would show 

 the bones of the hand, S. P. Thompson found the heaviest 

 metals made the best targets in X-light reflecting focus tubes. 

 The reason usually given is that light metals like aluminum 

 allow X-light to pass through them, this part of the light being 

 lost. Why should aluminum be transparent to X light if this 

 is an electromagnetic phenomenon .like ordinary light ? Max- 

 well's theory requires conductors to be opaque. Aluminum is 

 a good conductor and should be opaque to X-light. It is 

 transparent. If X-light is an electromagnetic phenomenon, 

 we must find some way of explaining the transparency of 

 aluminum. Consider first the solid atom theory. As the 

 nature of a substance depends on its atoms, conductors must 

 have opaque atoms if these are solid. If X light is an electro- 

 magnetic phenomenon it cannot travel through such solid 

 conducting atoms. If it passes through a metal with solid 

 atoms it must pass in the ether between them. If one metal 

 is more transparent than another, the more transparent must 

 contain more ether. On the solid atom theory how can we 

 get more ether in aluminum than in platinum ? The solid 

 atoms are of one size. There are about as many of them in 

 aluminum as in platinum, for the ratios of the atomic weights 

 are about the same as the ratios of the densities. There is not 



