22 



A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



filtered or with room air. A jet free from air currents should be most efScient, 

 ccst. par. Curiously, the maximum nucleation obtainable with jets lies just 



TABLE 4.— EFFECTS OF SUCCESSIVE EXHAUSTION. WATER NUCLEI. ESTI- 

 MATED NUCLEATION. 



Nucleations corresponding to successive coronas: 



below the maximum nucleation of atmospheric air as found in the winter observa- 

 tions. Probably this is a mere coincidence. 



THE IONIZATION OF WATER NUCLEI. 



6. Introductory. — In my report to the Smithsonian Institution (August, 

 1902) and elsewhere,* I pointed out the desirability of further investigations on 

 the Lenard ^ effect. While my work in this direction was in progress, a paper 

 due to J. J. Thomson ^ appeared covering similar ground. Nevertheless, I 

 shall venture to publish the following results, since the subject is looked at from 

 a somewhat different point of view, obtained from coronal and other measure- 

 ments. My chief purpose, however, was to find in what degree the theory given 

 in my experiment with Ionized Air * was to be modified to meet the conditions 



' Science, xvi, p. 633, 1902. 



' Lenard, Wied. Ann., xlvi, p. 584, 1892. 



' J. J. Thomson, "Experiments with Induced Radioactivity of Air, and on the Electrical 

 Conduction Produced in Gases when they Pass through Water," Phil. Mag. (6), iv, p. 352, 

 September, 1902. 



* Smithsonian Contributions to Knowledge, 1309, 1901. 



