Rays of Positive Electric it//. 575 



nitrogen to be observed on the screen ; a proof, it seems to 

 me, that different gases may be made by strong electric fields 

 to give off the same kind of carriers o£ positive electricity. 



Another result which shows that the positive rays are the 

 same even although the gases are different is the following. 

 The tube was pumped until the pressure was much too low 

 for the discharge to pass, then small quantities of the following 

 gases were put into the tube : air, carbonic oxide, hydrogen, 

 helium, neon (for which I am indebted to the kindness of 

 Sir James Dewar); the quantity admitted was adjusted so 

 that it was sufficient to cause the discharge to pass and yet 

 did not raise the pressure beyond the point where the phos- 

 phorescence is discontinuous. In every case there were 

 patches corresponding to <?/m=10 4 , e/m = 5 x 10 3 , and except 

 with helium these were the only patches ; in helium, in addition 

 to the two already mentioned, there was a third patch for which 

 e/m=2'5 x 10 3 . * 



I also tried another method of ensuring that at these low 

 pressures there were other gases besides hydrogen in the 

 tube. T filled the tube with helium, and after exhausting to 

 a fairly low pressure by means of the mercury pump, I per- 

 formed the last stages of the exhaustion by means of charcoal 

 cooled with liquid air. This charcoal absorbs very little 

 helium in comparison with other gases ; so that it is certain 

 that there was helium in the tube. The appearance of the 

 phosphorescent screen of tubes exhausted in this way did not 

 differ from those exhausted solely by the pump. 



The most obvious explanation of these effects seems to me 

 to be that under very intense electric fields different substances 

 give out particles charged with positive electricity, and that 

 these particles are independent of the nature of the gas from 

 which they originate. These particles are, as far as we know 

 at present, of two kinds : for one kind e/m has the value of 10 4 , 

 that of an atom of hydrogen ; for the other kind e/m has half 

 this value, i. e. it has the same value as for the a particles 

 from radioactive substances. 



This agreement in the maximum value of e/m at different 

 pressures is a proof that this is a true maximum, and that 

 there are not other more deflected rays not strong enough to 

 produce visible phosphorescence ; for if this were the case — 

 i. e., if the value of e/m for a particle that had never lost its 

 charge temporarily by collision were greater than 10 4 — we 

 should expect to get larger values for e/m at low pressures 

 than at high. 



I have much pleasure in thanking my assistant Mr. E. 

 Everett for the assistance he has given me in these ex- 

 periments. 



