Nolan — Ions produced in Air h/j liudio- Active Bodies. 45 



preseiil writer tines imt admii) are entirely abisent in liie case ol the pu-sent 

 experiments. 



As to the existence of separate groups of laige icns, woils vliicli is at the 

 present time being carried out in the Physical Laboiator}' fif L'ni^•ersity 

 College, using the method employed by Blackwood (the Zeleny method), is 

 in complete confirmation, as far as it has gone, of the previous work. Not 

 only does the Zeleny method indicate clearly the co-existence of sopaiate 

 groups of large ions, but the mobilities deduced by it aie in complete agree- 

 ment so far with those obtained by the M'C'lelland method. It is hoped to 

 present this new evidence and to deal with the whole question of large ions 

 in a future communication to the Academy. 



With regard to the small ions, the present paper is obviously incomplete. 

 The main results are presented pending a complete examination of the many 

 points which call for attention. 



The author wishes to thank Mr. F. E. Lewis, b.a., b.e., who prepared the 

 diagrams for this paper. For help and inspiration in this and other work 

 the author is deeply indebted to the late Professor M'Clelland. 



R.I. A. PROC, VOL. XX.KV, SKCT. A. [6] 



