C. Bants — Velocity and Stymcture of the Nucleus. 233 



ever, it is a question whether the total absence of solid solute 

 in experiments with acid solutions can be guaranteed. The 

 next evidence is perhaps better ; if it were a mere question of 

 fixed residue, then the neutral organic solutes like the sugars, 

 urea, glycerine, etc., should be quite as effective in producing 

 persistent nuclei as the saline solutes. Table I shows that this 

 is not the case. Finally since the pressure decrement of much 

 less than 2'^'" of mercury produces precipitation, the vapor pres- 

 sure excess at the surface of the nucleus is small, and quite 

 within the limits of reduction produced by solution. The 

 evidence from hygroscopic bodies in which dry residues are 

 out of the question, has already been given. § 6. 



Turning now to the electrical point of view, one notices at 

 the outset a marked similarity in the trend of the above results 

 to the researches of Lenard* on the electricity produced by 

 waterfalls and jets. He showed that pure water when prop- 

 erly comminuted by spraying was made electrically positive 

 while the surrounding air became electrically negative, that 

 these charges originated in the liquid in contact with air and 

 could be indefinitely increased with the intensity with which 

 the spray was projected against a solid obstacle. This is in 

 harmony with the conditions for producing the above nuclei. 

 Again, the electric manifestations stated for pure water were 

 totally changed in character by the addition of mere traces of 

 solute to the water. Thus in case of dilute salt solutions the 

 liquid on comminution became negatively charged, and the air 

 positively charged. As little as '005 per cent of salt was 

 sufficient to nearly wipe out the water effect. This then is 

 quite similar to the conditions of persistence of nuclei instanced 

 in the above tables. 



Lenard's explanation is in terms of the '' Doppelschicht," 

 which for pure water is conceived to be negative outward, and 

 for aqueous solutions and other bodies usually positive out- 

 ward, and due purely to voltaic contact. If this view is cor- 

 rect, i. e., if air in contact with pure water is invariably 

 negative by contact action no matter whether the surface is 

 plane or markedly convex, and if air in contact with salt solu- 

 tions is invariably positive, the solution being negative, then it 

 is the negatively charged nucleus (solution) which persists and 

 the positively charged nucleus (pure water) which is fleeting 

 or virtually non-existent. It follows, therefore, that condensa- 

 tion with subsidence is equivalent to a removal of negative 

 electricity provided the air charge is not simultaneously 

 removed. Cf. § 5. 



Brown University, Providence, R. I. 



*Lenard, Wied. Ann., xlvi, pp. 584-636, 1892. 



