114 Proceedings of the Royal Irish Academy. 



cases ; but we tire unable at present, in tlie absence of further information 

 from the experimental side, to go any further in the direction of correlating 

 the observed values of mobilities and charges. 



General Conclusions. 



The idea of the large ion as a rather loose group, originally suggested by 

 de Broglie and adopted^ to explain certain mobilities observed, is practically 

 forced on us by our observations of recombination between large ions and 

 small ions. The units out of which we have supposed the ions to be built, the 

 various homogeneous groups of ions which in so many cases accompany the 

 final more stable body, reappear when the ion breaks up under the action of 

 high temperature. The further complex stages observed in the case of 

 phosphorus ionisation appear when the ions are affected by the presence of 

 sulphur dioxide, ammonia, or sodium chloride. 



The large ions present in the atmosphere are possibly in great part 

 produced by the action of ultra-violet light on the moist gas. They carry 

 single electronic charges, and their constant of combination with small ions is 

 between 5 and 10 x 10"^ 



The greater part of the experimental work described in this paper was 

 carried out between the years 1916 and 1919 under the direction of the late 

 Professor McClelland. We wish to express our indebtedness also to Dr. H. 

 Kennedy, who has permitted us to make free use of his unpublished work. 



' J, J. Nolan, Proc. Roy. Soc, A, vol. xciv, p. 112, 1918. 



