IO CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



TABLE 5. Water nuclei from evaporation of fog particles precipitated on vapor nuclei 



in dust-free air Continued. 



*A11 conditions identical to the above, except that there is no primary exhaustion or fog precipitation 

 on vapor nuclei. The absence of all condensation at 18 shows that no nuclei come through the filter. 



8. Effect of changes of the drop of pressure up. The second part of 

 table 5 contains results in which residual water nuclei are captured at 

 drops of pressure from up=i& to 27 cm. At first the coronas do not 

 change ; eventually they decrease in a way to be referred to the increased 

 amount of water precipitated. Vapor nuclei are inefficient in the presence 

 of water nuclei. 



f The constancy of coronas after all nuclei have been caught through a 

 considerable range of values of dp, occurs here as elsewhere and has not 

 yet been fully explained. As the nucleation n varies with the precipi- 

 tation (m grams per cu. cm.),w T hile n increases with dp, the computed 

 values of n must also do so, thus conflicting with the observed fixed 

 coronal aperture. It is difficult to conjecture where the excess of water 

 precipitated goes to, even if we recall the slow change of 5 implied in 

 dcC'i/m or s^/ni = const. In some way, probably coincident with the rise 

 of temperature after adiabatic cooling, the excess of precipitation is again 

 removed before coronas can be observed. The efficiency of the fog 

 chamber virtually breaks down, as no more water is deposited when dp 

 increases. 



It follows in general that neither by the time loss nor by the effect of a 

 varying drop of pressure is the tendency of rapid evaporation to produce 

 persistent water nuclei materially influenced. It must, therefore, be an 

 occurrence of its own kind. 



