8 



issuing from the original radioactive material. And it looks 

 quite unlike a coincidence that similar comparisons can be 

 made in the case of the X-rays. The secondary cathode radia- 

 tions due to these rays have velocities which, at the least, are 

 of the same order as the velocities of the cathode particles in 

 the X-ray bulb. If we examine the table given by Innes 

 (Proc. Roy. Soc, Aug. 2, 1907, p. 461), and if we may be 

 allowed to adopt an interpretation differing somewhat from 

 the author's, but more natural, it seems to us, in view of the 

 conclusions of this paper, we find that the velocities of the 

 electrons emitted by all the metals are practically the same, 

 zinc being an exception, because it is unable to break up the 

 hardest rays. We find that the velocities range from about 

 6xl0« to 7-5xlO« for soft rays, and 6 x lO'-* to 8x10^ for 

 hard rays. Remembering that bundles of X-rays are very 

 heterogeneous, the natural conclusion seems to be that the 

 softest rays give the slowest speeds, and that the velocity of 

 the secondary rays increases with the hardness of the X-rays 

 from which they are derived. *2) Now the hardness of the rays 

 grows with the speed of the cathode particles in the bulb. 

 Is it then possible that the cathode particle is first set in 

 motion by the electromotive force in the bulb, strikes the 

 anticathode, and picks up a positive there, becomes neutral, 

 and is now called an X-ray, is subsequently stripped of the 

 positive, and becomes a secondary cathode particle, the iden- 

 tity of the negative remaining the same throughout, and its 

 speed invariable, or nearly so ? The difficulty comes in when 

 we try to consider the part played by the mass of the positive. 

 Probably it becomes necessary to consider it as small compared 

 to the mass of the negative. In many ways such a supposi- 

 tion would fit in very well. We should then understand why 

 the positive is so hard to isolate: also a radioactive atom, in 

 ejecting a y particle would not lose appreciably in weight. 

 Lilienfeld believes he has found the positive electron to be less 

 massive than the negative. (Deutsch. Phys. Gesell. Verb., 9, 7, 

 April 15, 1907.) 



And, again, may not the $ and y forms be interchange- 

 able at times ? A y particle, which had been stripped of its 

 positive, and become a secondary cathode, or /3 ray, would be 

 lost to measurement as a y ray ; and we should thus have an 

 explanation of how the y rays are "absorbed," and why the 

 absorption follows an exponential law. And in the same way, 

 if a j8 particle picked up a positive, it would disappear fix)m 

 view as a i8 particle, it would be "absorbed." 



(2) By independent experiment, Bestelmeyer (Ann. d. Phys., 

 xxii., p. 429, 1907) and Cooksey (Amer. Jour, of Science, Oct., 

 1907) arrive at the same conclusion. 



