14 CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



If the radius of residual water nuclei be taken as io~ 6 cm., the charge 

 needed would be roughly e = 6.3 X io~ 8 electro-static units per particle and 

 its potential would be about 18 volts. If about 200,000 of these droplets 

 or residual water nuclei are present per cubic centimeter (as were found 

 above), the charge would be about 4 coulombs for a cube each side of 

 which is 100 meters. If all the particles of the cubic centimeter were 

 brought to coalescence the size of the drop would be 58 X io~ 6 cm. at its 

 potential of about 63,000 volts. Finally, the electric contents of my fog 

 chamber should be about 30 electro-static units of quantity, and ought 

 thus, in spite of the moisture present, to be easily determinable. The 

 experiments showed only about o.^oX io~ 6 electro-static units per cubic 

 centimeter, less than the contents (o.88X io~ 6 ) in the room air without, 

 at the time; thai is, the average charge per nucleus was about 5X io~ 12 

 electro-static units, or less than i electron. Hence the electrical hypoth- 

 esis must be abandoned. It would in any case be improbable for the 

 charge to show so small a coefficient of decay as do the water nuclei. 



14. Statistical hypothesis. Under the circumstances it seems per- 

 missible to suggest an hypothesis of a statistical character; namely, that 

 the molecule of liquid water is composite, consisting of virtually more 

 volatile and less volatile constituents. Such a view is quite compatible 

 with the composite molecule observed in water vapor, where millions of 

 nuclei may be captured long before the molecule proper is reached, the 

 evidences of which are now beyond question. In case of fog particles, 

 when the evaporation is reduced to extreme slowness, we may conceive 

 that all groups of molecules evaporate together at about the same rate, 

 and that therefore the residue, i. e., the persistent water nuclei, are present 

 in least amount. On the other hand, when the evaporation is forced, or 

 accelerated by the heat due to compression, the more volatile constituents 

 of the fog particles evaporate faster than the less volatile, and there is a 

 correspondingly greater residue of persistent water nuclei, because of this 

 concentration of the less volatile molecular aggregates of water in each 

 fog particle. It follows also that relatively more persistent nuclei are 

 obtained by the evaporation of large fog particles than by the evaporation 

 of small particles, because a greater relative number of these droplets 

 would contain a sufficient number of the less volatile groups to persist; 

 i. e., the opportunities for concentrating the less volatile aggregates are 

 enhanced. Finally, it should never be possible to replace all fog particles 

 by the water nuclei derived from them. All of these deductions are in 

 keeping with the experimental evidence, as pointed out. 



