118 THE STRUCTUKK OF THE NUCLEUS. 



foroua ftuil its fleetness in vaiiisLiiig ; aii'l tliis will he seeu to be frequently the 

 case in the ex[>erinients with salt soliitiuus. Usually, however, small coronas 

 vanish more rapidly, under otherwise like conditions. 



The enormous lapidity with wliich the nuclei vanish in case of pure water 

 needs n(j further conuneiit. Mere standini; of the water in the receiver may at 

 times increase the persistence ol' coimias. 



i;}. Sodic thJoride. Stipfinsatiiration. — Four measurements (table 3) made 

 atrf^' =- 16 em., areavailal)le for standardization; viz.,.s':= 1.65, Lslf), ].")."», 1.40, from 

 wliich // — 47 Xs-' = 211, 175, 17"), I'Jit. Here as elsewhere a gradual diminution 

 of tlie nund)er of nuclei is apjiarent. and it is possible that at the outset some 

 unknown source of nuclei is still active. 



To compute the sizes of the particles, the equation now becomes d ^=. .2'2'i-^m, 

 and tiie corresponding grajdi is seen in figure 7. 



14. Tiiiii- Jossts. — Though the results are not smooth, the loss will not exceed 

 .3 particle |)er minute. ('/. figure 8. 



If). Kff'ect of shahintj. — The lesults hei-e are again pronounced and indicate 

 the most fertile cause of difficulties in the present investigation. The productivity 

 is much in excess of the eaily datum foi- UCl, being as liigh as 1(1-30 particles 

 per jerk, corresponding to the larger coronas resulting. 6/'. figure 8'. 



Hi. Calcic clilovids. Supermtnralioii.. Tims lossef<. — The coronal diameters 

 accompanying the normal pressure decrements of 16 cm. were, successively, 1.70, 

 1.75, 1.75, 1.70, 1.70. The average numbei' of particles is thus, ii ■= 47s* or about 

 240. From this the range of diameters for the otliei' pressure differences is com- 

 puted and the results given in table 4 and the graph, figure 9. 



The coefficient in case of the time losses is 1.3 particles per minute. 



17. Minimma j)res><vre decrement {>iiipevmivraiwir) for complete precipitntiim. 

 — Tlie .secon<l part of the table contains results with a new bearing, showing that 

 if paiticles are completely precipitated at a low pressure deci'ement, by repeated 

 exhaustion, they will also be absent at the higher pressure decrements. In other 

 words, the nuclei may be completely precipitated out at pressui'es falling suddenly 

 to less than 2 cm. below the atmospheric pressure. This affords a means of esti- 

 mating a superior limit for the size of tlie nuclei. Table 4 shows the number of 

 nuclei surviving from tlie same initial shaking, after eacli of the succe.ssive 

 exhaustions specified, pure filtered air lieing supplied between the operations. As 

 a iiile, two exhaustions are needed to completely remove the nuclei, even if caiv 

 he taken to wait for the subsidence of each fog. It follows, therefore, that 

 evaporation occurs abundantly, and at the moderately low pressure decrements, 

 about one half the nuclei escape by shifting their load. At the lowest pressure 

 decrements ('J cm.) four exhaustions were reijuired and the mean rate here is 

 about 43 particles diopped pei' exhaustion, or less than one tliii'd the total number. 

 If persistence were due to a retai'dation of exhaustion, tliis would not he the charac- 

 ter of the plieiiotneiion. The present lesidt, moreover, agrees with the data com- 

 puted for tiie size of particles, </, at the lower pressure decrements, the coronas 

 observed beiut' too small. 



