1907.] on Rays of Positive Electricity. 591 



carrier — that corresponding to — = 5 x 10^ — has disappeared. The 



presence of the nitrogen bands in the spectrum shows that nitrogen 

 is carrying part of the discharge, and yet there are no rays character- 

 istic of 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 of positive electricity. 



Another result, which shows that the positive rays are the same 

 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 pressm-e beyond the point where the phosphor- 

 escence is discontinuous. In every case there were patches corre- 



spondins^ to = 10^, ^ = 5 x 10^, and except with helium these were 

 ^ ° m m 



the only patches ; in helium, in addition to the two already mentioned, 



there was a third patch for which — = 2*5 x 10^. 



m 



I also tried another method of ensuring that at these low pressures 

 there were other gases besides hydrogen in the tube. I filled the 

 tube with helium, and after exhausting to a fairly low pressure by 

 means of the mercury pump, I performed the last stages of the ex- 

 haustion 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 — has the value of 10^, that of an atom of hydrogen ; 

 for the other kind — has half this value, i.e. it has the same value as 



771 



for the a particles from raidioactive substances. 



This agreement in the maximum value of — at different pressures 



m 

 is a proof that this is a true maximum, and that there are not other 

 more deflected rays not strong enough to produce visible phosphor- 

 escence ; for if this were the case — i.e. if the value of — for a particle 



m 



