50 VAPOR NUCLEI AND IONS. 



an increase of size of the efficient air nuclei and a decrease of their number. 

 Hence if we were to fancy that the colloidal nucleation of air responds 

 to its own radiant environment, this would have to be special in kind. 



Recently I have made similar tentative inquiries as to whether the 

 ions and persistent nuclei might not be regarded as colloidal nuclei 

 aggregated by kinetic pressure, corpuscular or undulatory; for in view 

 of the occurrence of pronounced secondary action within the fog chamber, 

 the radiation at any point must be considered as sufficiently the same in 

 all directions to be equivalent to a Lesage medium. It is then possible 

 to account for the nucleation in any ionized field, for fleeting and per- 

 sistent nuclei, for condensational differences of positive and negative 

 ions, for fleeting nuclei otherwise identical but respectively charged and 

 uncharged, for the destructive effect of low pressure and the counter- 

 action in strong ionized fields, for electrical differences in the effect of 

 ultra-violet light and of X-rays, etc., with a single straightforward 

 hypothesis. 



While such a view may be worth a statement, it would at the outset 

 encounter very determined opposition; and the distinctive or differen- 

 tiating evidence to sustain it is uncertain. Briefly, if we admit that 

 with ions sufficiently large and sufficiently numerous, relatively speaking, 

 the colloidal nuclei are virtually non-existent (so far as the fog chamber 

 is concerned), since the former capture all the available moisture, most 

 of the phenomena of nucleation admit of interpretation, and additional 

 hypotheses, however alluring, are not called for. Moreover, so long as 

 the representative colloidal nuclei are definitely smaller than the smaller 

 ions, even in the strongest electrical field in other words, if what may 

 be called the shattering action of strong fields always fails to reveal 

 ionized nuclei as small as the representative colloidal nuclei the special 

 interpretation is not warranted. 



In conclusion, if we asked what is the most important outcome of 

 researches of the present character, I should refer to the appearances 

 obtained, indicating that a gas, or at least a moist gas, far from being a 

 uniform system, behaves like an assemblage of nuclei which decrease in 

 size and increase in number as the molecular dimension is approached. 

 Every group of nuclei is none the less a structurally essential part of the 

 gas and (be the number of groups few or many) is at once restored if 

 withdrawn, while the molecule itself is distinguished among the many 

 nuclei of its own kind by the maximum frequency of occurrence. 



In the above cases (fig. 25) the occurrence of nearly identical slopes 

 for colloidal nuclei and for strong ionization may thus be regarded as 

 the initial branch of a law of distribution of sizes given by the theory 

 of dissociation. 



