RESIDUAL WATER NUCLEI. 



97 



60 



50 



40 



SO 



ZO 



10 



.1 



.3 



.1 



FIG. 30. Number of residual water nuclei obtained from rapid evaporation of fog 

 particles and found at different small adiabatic drops of pressure dp/ 'p. 



FIG. 31. Number of residual water nuclei obtained from rapid evaporation of fog 

 particles in a partially exhausted fog chamber and caught at different small adiabatic 

 drops of pressure dp/p. 



When the drop dp 3 is as low as 2 cm., the number of water nuclei 

 is relatively small, though at 5 cm. the maximum is already reached. 

 Unfortunately, therefore, the range of marked variation of n lies below 

 a few centimeters of dp 3 , wherefore the coronas are too filmy and large 

 to admit of easy identification, unless a special immense fog chamber 

 is constructed for small exhaustions. So far as these experiments go, 

 however, the appearance is rather such as recalls the distribution curves 

 for ions and for dust-free air; in other words, the water nuclei are prob- 

 ably of all sizes within certain limiting dimensions, like the ions. 



In the third series of table 41 the attempt is made to further study 

 these large, filmy coronas. They may be recognized with certainty here 

 and are throughout of the green-blue-purple type, corresponding to 

 about 100,000 nuclei under normal expansions. At the low exhaustions 

 used, however, they correspond to 10 or 15 thousand nuclei per cubic 



