20 INAUGURAL ADDRESS. 



gamma and X rays cannot. This shows that the former are charged 

 electrically, and, since pulses cannot carry charges, we conclude that 

 the rays are material. The gamma and X rays are not acted on by 

 electric and magnetic jfields ; they are therefore uncharged. This does 

 not prove them to be immaterial — to be pulses, in fact ; they may be 

 material particles without charge. The simplest conception of such a 

 material particle would be one negative electron with its positive 

 counterpart. 



Again, it is important to remember that when X rays were first 

 discovered nothing was known of material radiations capable of pass- 

 ing through matter in straight lines, and the remarkable power of 

 penetration which the rays were found to possess was sufficient to put 

 out of court any suggestion that they might be material. That 

 objection has vanished now. Even the electrified beta rajs possess the 

 property of penetration ; some of the electrons in a stream of such 

 rays, projected against a metal sheet, are foimd to have passed 

 through, apparently without being aflfected in any way. When we 

 remember that such electrons as have been swung aside out of the 

 stream owe the eft'ect to the strong influence of their electrical charges, 

 it is natural to suppose that if the charges Avere neutralised by the 

 attachment of the corresponding positives, the penetrating power would 

 be greatly increased. Thus, the same simple hypothesis which ex- 

 plains the independence of electric and magnetic fields explains also 

 the extraordinary penetration of the gamma and Rontgen rays. Nor 

 does it stop short here. The movement of the rays in straight lines, 

 without dispersion of their energy, is at once made clear; the rays 

 resemble material particles in their behaviour simply l)ecaiise they 

 are such, and there is no need to invent a special aether to cover the 

 case. And, again, the ease with which the energy of the cathode ray 

 may change into that of the Rontgen ray, and back again, is under- 

 stood. It is simply that the negative electron picks up its positive 

 countei'pai't, and again puts it down. The electron of the cathode 

 stream is driven against the surface of the anti-cathode, and pene- 

 trates the atoms there. If the atom consists, as is generally supposed, 

 of a number of similar electrons embedded in a quantity of positive 

 electricity of little massiveness, it is easily to be imagined that in one 

 of these deflections its temporary entanglement may be so great that 

 it may pick up the neutralising amount of positive before emerging. 

 Thus, instead of the negative cathode particle we now have a neutral 

 pair, incapable of deflection by electric or magnetic fields and endowed 

 with far more power of penetration than the original cathode paii;icle. 

 Yet the neutralising positive may be torn away again from the electron 



