Natures of various Electric Radiations. 449 



Added July 18. — Since this was written several important 

 papers have appeared, with which the outlined theory seems 

 to me to be in harmony, 



I have supposed it possible for positive electrons to be 

 detached from atoms of matter in the X-ray tube, and to 

 be sent out in company with negative' electrons, one of each 

 going to the formation of a neutral pair. Now J. J. Thomson 

 has just shown (Phil. Mag. May 1907) that the canal-rays 

 consist of positive electrons, which may be H or H 2 or He, 

 according to circumstances ; and that these appear no matter 

 what the material is, in the tube. It will be remembered 

 that Villard (Ions, Electrons, Corpuscules, p. 1022) was so 

 impressed with the continual presence of hydrogen in vacuum- 

 tubes, that he supposed the cathode particles to consist of 

 hydrogen, until accurate measurements of the mass and 

 velocity of the particles were made. He was largely influ- 

 enced by the reducing action of the rays. After all, it may 

 be that H is produced where they strike, and that Villard's 

 observations can be explained in this way. Sir William 

 Ramsay (Journ. Chem. Soc. May 1907) has shown that there 

 is an excess of hydrogen in water decomposed by radium 

 emanation ; but the circumstances are too complicated to 

 make the connexion more than a possibility at present. 



H. W. Schmidt has arrived at the conclusion (Pliys. Zeit. 

 June 1907) that the " secondary " radiation caused by (3 rays 

 striking aluminium consists of scattered primary rays : this 

 is in agreement with the argument stated above. He has 

 also shown that undeflected /3 particles lose no speed in 

 passing through a metal plate. This implies either that the 

 energy required to produce ions does not come from the 

 ft particle or that the /3 particle does not produce ions until 

 it is deflected. There seem several difficulties in the way of 

 the latter supposition : though it is of course a possibility. It 

 seems to me probable that the /3 particle rarely produces more 

 than one ion from a traversed molecule, but that an a particle 

 may produce many : and that initial recombination is to be 

 explained in this way. Kleeman has pointed out, in his 

 Royal Society paper, that an « particle which has lost several 

 ions has not yet been observed ; but it is to be remembered 

 that such a molecule would probably dissociate at once, 

 and it is well known that the a particle does produce 

 dissociation. 



