94 Proceedings of the Royal Irish Academy. 



up charges gradually from the natural ionisation of tlie space iu vrhieli they 

 are confined. li supplied with small ions in large quantity, the process of 

 charging vrill be more rapid, and ia either ease the resulting body behaves in 

 all respects like the origiaal ion. 



In the ordinary Bunsen flame the two essentials, the nucleus-forming 

 material and the small ions, are always present, and large ions are always 

 found in great niunbers. Aitken has shown, however, that a flame of pure 

 hydrogen wiU produce no nuclei ; and de Broglie^ has shown that a flame of 

 pure and dry hydrogen burning in a cool chamber will produce no large ions. 

 Here it is clear that the original nucleus-forming material has been eliminated. 

 Dr. H. Kennedy,- working in this laboratory, has found that an ordinary non- 

 luminous flame fed with filtered aii" and coal-gas, burning in a vessel of fused 

 quartz which had undergone long preliminary heating, produced no large ions 

 or nueleL Using Aitken's counter, one nucleus per e.c. of aii- could easily he 

 detected, but no indications of any were found. Kennedy found that the 

 luminous gas-flame burning in the same fashion always gave a copious supply 

 of large ions and nueleL Presumably the incomplete combustion of the 

 limiinous flame favours the escape of the nucleus-forming materiaL In the 

 absence of the nuclei the small ions from the non-luminous flame rapidly 

 recombine and vanish. 



These experiments show the necessity for the presence of the nucleus- 

 forming material as an essential to the formation of the large ion. It can 

 also be sho\vn that nuclei may be produced, originally tuicharged, which, 

 wlien small ions are supplied, are transformed into lai-ge ions. Tlius 

 de Brc^lie' has shown that nuclei may be produced by heating moist pumice. 

 These nuclei could be converted into large ions when small ions were supplied 

 by means of radium. McClelland and Mc Henry* have shown that the nuclei 

 produced by the action of ultra-^'iolet light on a moist gas or by the heating 

 of glass and metal surfaces may be converted into large ions when small ions 

 are supplied by means of uranium. The large ions thus produced appear to 

 be identical with those produced in other ways. We have thus e\"idence 

 from two sides of the conditions necessary for the formation of the large ion. 

 Nuclei set free from a surface by heat remain uncharged in the absence of a 

 flame or other source of ionisation. Small ions produced in a flame recombine 

 and vanish in the absence of nuclei produced from the flame or some object in 

 its \icinity. 



1 de BrogUe, C. R. 151, p. 67, 1910. 



- Unpublished work. 



^ de Broglie, Ann de Chimie et de Physique, 16, 1909. 



* McQelland and McHeniy, Proc. Roy. Dublin Soc, xri, p. 282, 1921. 



