RESIDUAL WATER NUCLEI. 117 



decidedly smaller for ions in the first exhaustion than for vapor nuclei. 

 The charged nuclei are therefore destroyed in greater number by the 

 evaporation of fog particles precipitated on them. When the number 

 of nuclei is large (io fi ) this is also true in subsequent evaporations, though 

 the contrast is less marked. 



Another question which comes up for settlement is this: Whether 

 the fog particles which are represented by nuclei after evaporation are 

 above a certain critical size, and those particles which vanish are below 

 it. This is hardly probable, because all the fog particles contributed to 

 the same corona and because it implies an enormous inequality in the 

 fog particles of the first exhaustion, considering that 45 to 85 per cent 

 of these vanish in the different cases cited. For the present purpose it is 

 sufficient to write Js' = o.oo32, where s' may be taken from tables 46 

 and 47. These results for the diameters of fog particles are given in 

 table 48. They are constructed graphically in fig. 37, a, b, for ions, and 

 in fig. 37, c, d, for water nuclei. 



Fig. 37, a, containing series 4 to 8 for ions and small nucleations below 

 500,000, suggests that x may change abruptly when d = 0.0006 cm.; 

 while fig. 37, b, for ions and large nucleations, io 6 has the same appear- 

 ance at d = 0.0005 cm - ^ is seen, however, that this is nothing more 

 than the transition from the first to the second evaporation, the former 

 being so much more efficient. 



Fig. 37, c and d, for large and small nucleations of vapor nuclei, has 

 the same character. In c, for instance, there is an abrupt change below 

 40,000 nuclei. But the case is again one instancing the paramount 

 importance of the first evaporation. There is, however, no doubt of an 

 outstanding effect due to the number or the size of nuclei. The co- 

 efficient of survival x decreases as the number of nuclei increases, or 

 better, as their size diminishes. Thus, if the comparison be restricted 

 to the first evaporation fig. 37, e, 



Ions. 



Vapor nuclei . . 



38 37 37 

 io 2 Jt: = 4O 25 29 

 io s d= 39 38 

 io?x= 55 46 



26 26 



16 21 



23 23 



35 25 



21 22 

 19 21 



21 21 centimeters. 

 16 20 



centimeters. 



from which the increase of x with the size of particles is put beyond 

 question and the larger coefficient of survival for vapor nuclei as com- 

 pared with ions is again apparent. Whether the peculiar features of the 

 curve (fig. 37, c), which reappears in each case, have a definite meaning 

 must be left to conjecture; but in most of the curves a, b, c, d, e, the 

 occurrence of maximum x is in evidence. 



69. The loss of nuclei actually due to evaporation. It is finally to 

 be shown that the peculiar loss of water nuclei resulting after evapora- 

 tion of fog particles precipitated upon ions is due to this evaporation 



