C. Bancs — Ionization of Water Nuclei. 119 



essential difference that whereas the current in the first case 

 obeys Ohm's law, roughly, it does not do so in the second, being 

 more and more independent of the electromotive force as E 

 increases above about 15 volts per cm. Corresponding to this 

 the coronas for water nuclei terminate with the ninth in my 

 series (5000 nuclei, § 5), whereas in case of phosphorus they go 

 to indefinitely higher orders beyond the first (3 X 10 5 nuclei) in 

 the series. Parallel to this there runs a difference in the size 

 of nuclei. The inference is warranted that phosphorus nuclei 

 are small as compared with water nuclei, inasmuch as the latter 

 owe their origin to mechanical conditions (evaporation from 

 gross fog particles), while the phosphorus nuclei arise under 

 chemical conditions and molecular dimensions. 



Finally, in direct measurements made by the steam jet method 

 (Experiments with Ionized Air, chap, iii), the velocity of the 

 phosphorus nucleus in the absence of an electric field was 

 actually shown to be of the order of ionic velocities in air, 

 while with experiments* since made with water nuclei 

 •001 to "01 cm. / sec. are average orders of values depend- 

 ing on the concentration of the solution. Experiments are in 

 progress to determine the velocity, Jc, with the identical water 

 nuclei under discussion in the above paragraphs ; but the data 

 in hand are sufficient to warrant the use made of the hypoth- 

 esis. 



In other respects there is great similarity in the behavior of 

 the two types of nuclei. The enormous charges or ionizations 

 at the beginning vanish to a residuum of a few per cent in a few 

 minutes, if confined by a receptacle, while the nuclei are not 

 affected either as to number or condensational properties by 

 the presence or absence of the primitive charge. 



16. Condensational effect of Negative Ionization. — In none 

 of the experiments, either with the neutrally ionized phos- 

 phorus emanation (where the ionization was tested after 

 partial condensation and subsidence of fog particles) nor with 

 the negatively ionized solutional nuclei is there evidence that 

 negative ions are more active as condensation nuclei than 

 positive ions. The electrical conditions vanish to a few per- 

 cent almost at once, while the nuclei are relatively permanent. 

 Experiment makes it improbable that the small residuum of 

 charge can have any appreciable bearing on condensation ; 

 witness the identical behavior of water nuclei when used 

 immediately after production and highly charged, and when 

 used some time later, after the charge has certainly left them. 

 Moreover the charges vanish proportionately, which they 

 would not do if the negative ions had a greater affinity for 



*This Journal (4) xiv, p. 225, 1902; cf. forthcoming memoir on ''The 

 Structure of the Nucleus," Smithsonian Contributions, 1902. 



