76 IONISATION OF GASES [OH vn. 



after an expansion, while the four- fold supersaturation 

 is still exceeded, no doubt they will form nuclei for 

 the condensation of drops without any pause at the 

 ion stage. But in the ultraviolet-light experiments 

 I have no doubt that the electrons, or all but an 

 insignificant proportion of them, had been loaded up 

 and had existed as ions before the expansion was 

 made." 



The next chapter contains an account of what are 

 probably the most important experiments yet made 

 in the Cavendish Laboratory. 





