IOO CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 

 TABLE 42. Sizes of residual water nuclei Continued. 



1 Radium in place; ions active in presence of water nuclei. 



2 Radium off. 



When the relatively large nuclei are caught at the very low drop 

 of pressure, a higher drop applied in turn always reveals a relatively 

 large number of water nuclei, apparently too small to have been caught 

 in the first exhaustion. This evidence must also be used with caution, 

 because evaporation in the filmy coronas, observed in the first instance, 

 is liable to be a marked feature. 



If the graphs of fig. 31 be prolonged until they intersect the axis at 

 about # = 0.05, the limiting superior diameter of water nuclei may be 

 estimated from the Kelvin-Helmholtz equation. Regarding the super- 

 saturation to be about 5 = 1.15, the amount of adiabatic cooling as far 

 as 9, the maximum diameter for the present series would be about 

 d = 2 X io~ 6 cm. In the above cases where the condensation began below 

 2 cm. (say at about i cm.) the maximum diameter than d = 25 X io~ 6 cm. 



One may notice, however, that the effect of temperature enters abso- 

 lutely into Helmholtz's equation, so that if the minimum volume of 

 expansion could be found it would be worth while to compute d carefully. 

 5 decreasing rapidly implies a corresponding rapid increase of d. 



In series VII and VIII, made at a somewhat later date, high exhaus- 

 tion and (incidentally) relatively high temperatures occur. The data are 

 also given in fig. 2, but they show no definite tendency. There remain 

 for discussion series IV and V, in each of which the filter cock was open 

 as widely as permissible and in which the number of water nuclei result- 

 ing from more rapid evaporation is often twice as large as heretofore. 

 In each of these cases the nucleation decreases very definitely and 

 rapidly with the exhaustion, as the numbers of nuclei were not only 

 large, but their sizes distributed over a wide range of values. 



