RESIDUAL WATER NUCLEI. 



95 



exhaustion, when the fog particles corresponding to s a have subsided, 

 leaving (by natural evaporation) the residual water nuclei corresponding 

 to the corona of any diameter 5^/30, behind. 



TABLE 40. Experiments with residual water nuclei. Bar. 76 cm.; temp. 14 C. 



Natural evaporation. 



'wo; 2 gbp. 



Table 40 shows that for initial coronas of the same size, 5 = 6.9, 

 residual coronas 5 = 2.7 an d 3 . o do not differ sufficiently to make the 

 evidence decisive. Less than one-tenth the original number of ions are 

 represented by water nuclei, the remainder having vanished by sub- 

 sidence with the fog particles or otherwise. There does not seem to be 

 any certain difference between the behavior of vapor nuclei and of ions, 

 so far as these experiments go. The large number surviving in the first 

 instance (small initial corona), as compared with a smaller number in 

 larger coronas, is striking. 



61. Rapid evaporation of fog=particles. In table 41 the filter cock 

 is left slightly open in order that the water nuclei may be increased. 

 The fog-chamber is initially at barometric pressure. The initial pressures 

 of the vacuum chamber are = 76.723.6 cm., to catch the ions 

 produced by weak radium and numbering about 100,000. The pressure- 

 differences are then reduced successively to the values to catch the water 

 nuclei left after the accelerated evaporation specified. The exhaustion 

 drops from p and pdp' as initial pressures in fog chamber and in 

 vacuum chamber to pdp 3 , the final common pressure in both, while 

 x = dp 3 /p is a convenient datum for the comparison of the water nuclea- 

 tions n. These have been corrected for the temperature t of the fog 

 chamber, more water being precipitated as / is higher and for volume 

 expansion from v at t to v l at / r 



