232 €. Bancs — Velocity and Structure of the Nucleus. 



sliaking and its relation to the order of values found in the 

 direct experiments with phosphorus nuclei given in Table II, 

 is accounted for by the thermodynamic hypothesis for their 

 occurrence, which makes them particles of concentrated solu- 

 tion. The size of the nucleus for a given solvent depends 

 essentially on the extremely small mass of solute which it hap- 

 pens to contain. It is larger when shaken from the more 

 concentrated dilute solutions than from the weaker solutions, 

 because the critical density is reached in the former case with 

 less evaporation and the capillary increment of vapor pressure 

 to be compensated is at the same time smaller. 



Thus it is quite reasonable to suppose that the nucleus 

 obtained from phosphorus or other emanations will be smaller 

 and therefore more mobile than the nucleus shaken out of the 

 more concentrated dilute solutions, but not so small in general 

 as the nuclei shaken. out of pure water or any other j)ure sol- 

 vent, in which the amount of solute is an actually vanishing 

 quantity. To carry out this comparison one should eliminate 

 the peculiar features of water and use the same neutral solvent 

 in both cases : but if the above results for benzol in Tables I 

 and II are brought together, the same inferences follow. 



9. Conclusion. — Among the tenable hypotheses, each of 

 which has some peculiarit}^ in its favor, the above paragraphs 

 are believed to sustain the inference that condensation nuclei 

 in a nearly saturated medium are concentrated solutions. In 

 proportion as the medium is less saturated, they may pass into 

 the dr}^ solute if such a one is present. The conditions of 

 equilibrium which are supposed to intervene are given in § 5. 

 Evidences in favor of this point of view are varied. In the 

 first place the velocity and therefore the size of the nucleus, no 

 matter of what origin, varies with the medium in which it is 

 suspended or is generated. Two mechanical suggestions may 

 be offered in explanation : either the nucleus condenses more 

 or less vapor spontaneously as assumed above, or the nuclei 

 themselves cohere into greater or smaller clusters, depending 

 on the medium. I pointed out that the latter case calls to 

 mind the suspension of clays, etc., in water or other liquids. 

 The endeavor to refer the differences to specific inductive 

 capacity or to the ionizing properties of the liquids breaks 

 down with such solvents as acetone. 



Of all the nuclei tested, those produced by shaking seemed 

 to be simplest as to their origin and therefore best adapted to 

 throw light on the subject. At first sight such a nucleus 

 should be the dry residue left after evaporation ; but the effi- 

 ciency of gaseous solutes like HCl, etc., shows that a solid 

 solute is not necessary. In view of the astonishingly small 

 quantity of solute which suffices to produce persistence, how- 



