8 



Proceedings of the Royal Irish Acudemii. 



Verji Large Iciis. 



An iiivesLigatiou as to whether there were any slower ions than that 

 of mobility 'OOOlo was carried out. Undried air was used, because with it 

 we get slower ions than with dried air. A number of wide tubes were 

 connected up in the apparatus between the phospliorus tube and the mobility 

 tube to increase the time between formation and measurement. A slow 

 gasometer blast was u.sed with the same object. For some of i,he experiments 

 a mobility tube having a specially long terminal was used in order to examine 

 the extremely low mobilities. The results obtained are as follows : — 



Table IV. 





•00032 



•00014 



•O0008S 



•000049 





•0002!) 



•00014 



■000088 



•0O00.V2 







•00015 



•000088 



•0000.55 







•OOOIG 



•000087 



•0000.10 







•00014 



•000088 



•0000o.i 







•0001.5 



•000077 



•000047 







•00016 f 



•000082 

 •dOOO!l7 ? 

 •0000!»1 ? 

 •OOOOttl ? 



•000011 1 :- 



•0000.^.1 

 •0000.'>7 

 •000043? 

 •000052 :- 



Menus, 



•00031 



•000 1.") 



•000085 



•000053 



Tiine-inteivala of 3, 5, 9, and i:'> minutes were used. Two ions of 

 lower mobility than -OOOlo were discovered. These ions are not present 

 in measurable quantity five minutes after the foimalion of the ionisation ; 

 they appcareil in the experiments conducted witli nine minutes as time- 

 interval. The numbers and curves giving these last two ions were not quite 

 as satisfactory as previous numbers. Tliis was perhaps due to the extreme 

 conditions under which the experiments were carried out. No attempt 

 was made to find slower ions than that of mobility OOOOoo. There is 

 nothing to indicate that this ion is the largest that is formed, 'i'he quantity 

 of electrification due to these slow ions is extremely small compared to 

 electrification due to any of the other ions at the short time-intervals. If the 

 ions of mobilities 000085 and 00005.3 are present at the short time-intervals, 

 they are present in relatively minute quantities. The most probable explana- 

 tion of their appearance is that they are gradually formed by grouping. It 



