296 Scientific Proceedings, Royal Dublin Society. 



II. — Nuclei deiven off Glass Tubes by Heat. 



If a glass tube be heated while air is passing through it, uncharged 

 particles are given off which can be charged by passing over uranium oxide. 

 The apparatus previously described was used also in these experiments, the 

 glass tube examined being included between the cotton-wool filter and the 

 quartz tube. A small quantity of charged particles was also given off when 

 a tube was heated. 



The tube was generally heated with a luminous gas flame extending over 

 about an inch of the tube. The presence of the nuclei was demonstrated by 

 an increase in the uranium current just as described in the case of the nuclei 

 produced in moist air by ultra-violet light. The emission of the nuclei fell 

 off rapidly, almost ceasing in about ten minutes generally, the current 

 registered falling off to the value of the uranium current alone. The effect 

 reappeared, however, on heating a cool place on the tube. 



Thus in one experiment the following numbers were obtained : — 



Small ion current (uranium alone) . . Oi = 19'8 



Current of nuclei driven by heat from glass and 



charged by the uranium ions . . 62 = 90'9 



After ten minutes' heating . . .02 = 20'8 



The large increase in the current would lead us to expect that the nuclei 

 are of great size. An attempt was then made to plot a current voltage 

 curve. Owing to the fatigue effect it was necessary for each reading to heat 

 a new place of the tube, beginning at that part furthest from the end where 

 the air entered. The charged ions driven off the tube by heat were removed 

 to earth by a second ionization tube as above described, so that the total 

 increase in the current is due to the uncharged nuclei. Saturation occurred 

 at 280 volts, giving a mobility of -0044. The curve also indicated the 

 presence of a smaller ion of mobility about •016. The mobility "0048 was 

 obtained in another experiment. 



Another experiment on a different tube did not give saturation at 400 

 volts— the highest voltage then available. This indicated an ion of mobility 

 less than •0028. The experiment was repeated, using a longer terminal, and 

 the mobility •OOIS obtained. 



The nuclei obtained by heating glass tubes are much more numerous than 

 those produced by ultra-violet light in moist air. In the latter experiments 

 some indications were always found of unattached small ions, whereas the 

 nuclei driven off by heat from glass tubes were so numerous that every small 

 ion attached itself to a nucleus before reaching the terminal. 



The tubes which lost on heating the property of emitting uncharged 



