Rays of Positive Electricity. 569 



mately constant, while the values of e/m range from zero at 

 the undeflected portion to the value approximately equal to 

 10 4 at the top of the deflected band. This value of e/m is equal 

 to that for a charged hydrogen atom, and moreover there 

 was no specially great luminosity in the positions correspond- 

 ing to e/m=10 4 /i4 and 10716*, the values for rays carried 

 by nitrogen or oxygen atoms, though these places were care- 

 fully scrutinised. As hydrogen when present as an impurity 

 in the tnbe has a tendency to accumulate near the cathode, 

 the following experiment was tried to see whether the Kanal- 

 strahlen were produced from traces of hydrogen in the tube. 

 The discharge was sent through the tube in the opposite 

 direction, i. e., so that the perforated electrode was the anode, 

 the electric and magnetic fields being kept on. When the 

 discharge passed in this way there was of course no lumi- 

 nosity on the screen ; on reversing the coil again so that the 

 perforated electrode was the cathode, the luminosity flashed 

 out instantly, presenting exactly the same appearance as it 

 had done when the tube had been running for some time with 

 the perforated electrode as cathode. 



The fact that a spot of light produced by the nndeflected 

 positive rays is under the action of electric and magnetic 

 forces drawn out into a continuous band was observed by 

 W. Wien, who was the first to measure the deflexion of the 

 positive rays under electric and magnetic forces. The values 

 of e/m. obtained from the deflexions of various parts of this 

 band range continuously from zero, the value corresponding 

 to the undeflected portion, to 10 4 , the value corresponding to 

 those most deflected. Wien explained this by the hypothesis 

 that the charged particles w T hich make up the positive rays 

 act as nuclei round which molecules of the gas through which 

 the rays pass condense, so that very complex systems made up 

 of a very large number of molecules get mixed up with the 

 particles forming the positive rays, and that it is these heavy 

 and cumbrous systems which give rise to that part of the 

 luminosity which is only slightly deflected. I think that the 

 constancy of the velocity of the rays, indicated by the straight 

 edges of the deflected band, is a strong argument against this 

 explanation, and that the existence of the negative rays is 

 conclusive against it. These negatively electrified rays, which 

 form the faintly luminous portion of the phosphorescence 

 indicated in fig. 6, are not cathode rays. The magnitude of 

 their deflexion shows that the ratio of e/m for these rays, 

 instead of being as great as 1*7 x 10 7 , the value for cathode 

 rays, is less than 10 4 . The particles forming these rays are 

 thus comparable in size with those which form the positive 

 rays. The existence of these negatively electrified rays suggests 



