THE STRUCTUlilC OF TUE NUCLEUS. 



83 



tribiition of nuclei, and reach a maxiiimia diatiietei', Itoim which they slowly decrease 

 indefinitely. Violent agitation (shaking) of the vessel and contents diminishes the 

 number of nuclei to a fi.ved minimum. The vessel is thus [martially cleansed by mere 

 shaking. The following are a few data : 



TABLE 9.— SIZES OF CORONAS IN BENZOL VAl'OR. EXHAUSTION, 76-58 cm. 

 VESSEL, 23 cm. IN DIAMETER. GONIOMETER RADIUS, 20.1 cm. DIAME- 

 TER OF DROPLETS, r/ IN cm. (/=.ooi44A. 



Thus, the white center of the corona originally exceeds 2 in diametei', while 

 the coronas left after shaking is somewhat over 1" in diameter. If .s is the chord 

 subtended by the a[ierture on the goniometer, the diameter of the particles are 

 found from h— 1.44 X 10" ^/.v, and the large size indicates that relatively few were 

 present. For reasons given above (Clhapter III, §§ 4, 5), the absolute ninuber of 

 particles cannot be found. 



The semi-annular coronas with sliaip horizontal demarcation make it possible 

 to measure the speed of diffusion of the nuclei upward. As showu in the figure, 

 the source of the nuclei is a couche very near the surface of the lake, a, (Chapter 

 III, Fig. 2), aud the vessel is left without interference for different lengths of time. 

 Usino- the globe 23 cm. in diameter, with a lake of benzol about 10 c-m. in diame- 

 ter, the rise°(roughly estimated) was about 1/3 of the height in 5'", 1/2 in 10'", and 

 3/4, the full height, in 18"\ The rates would thei'efore be .03, .02, .02 centinis. per 

 seco'nd, respectively. The experiment repeated with fresh benzol showed similar 

 results' After purifying the vessel and waiting 2 houi's, a magnificent multi- 

 annular corona (an evidence of exceptional homogeneity) showed itself, but van- 

 ished too soon for measurement. Cleaning and waiting for an additional half hour, 

 .* = .52, ^/= .0028 cm. was found. The following data were now investigated for 

 the rate at which these apparently spontaneous nuclei diffuse upward : 



Time elapsed, 5'" 

 10'" 



15'" 

 20"' 



Rise, 7 cm. 



9 cm. 



13 cm. 



17 cm. 



