THE STRUCTURE OF TIIE NUCLEUS. 



25 



The description of other apparatus (drums) specially adapted for axial colors 

 will be given in § 1 it. 



n-^ 



i^ 



^ 



a 



Cf= 



Fiff. J. f" Fig. la 



9 



^ 



T 



WCr 



jL 



Fig. 2. 



-..E - 



ffi 



Fig. d 





Fig. I. — Condensation Tube. Fig. 2. — Condensation Disc. 

 Fig. 3.— Condensation Globe. 



RESULTS I'OR CORONAS. 



6. General character of the plieiiomena. — As a whole, the diffi-action pattern in 

 homogeneous light is a contraction inward of dark rings, in proportion as the 

 pai'ticles duiing the course of exhaustion of the nucleated moist air grow lai'ger. 

 This motion is almost instantaneous on sudden exhaustion, but may be made 

 visible on gradual exhaustion. The I'ings, moreover, which are at first very diffuse, 

 contract as the exhaustion proceeds to small, sharper diametei's. Ordinary coronas 

 may be seen even when the precipitate is rainlike. 



The occurrences, however, are by no means a succession of ordinary coi'onas 

 {normal coronas, I shall call them), like those produced by lycopodiura. The 

 initial and particulaily brilliant coronas corresponding to finer particles have 

 colored central fields, and it is only after many exhaustions that the normal white 

 centered corona is reached. If the nucleation is very intense the coronas are apt 

 to be distorted with certain vapors and to tend to become sti-atified. Frequently 

 (and here even with watei' vapoi-) the colors mount from the pool of liquid below. 

 These irregularities occur more easily with hydrocarbons like benzine, etc., which 

 loads the nuclei more heavily and maintains larger nuclei than water. It is 

 occasioned by the subsidence of loaded i)articles, I'apid as compared with their rate 

 of diffusion when unloaded. On shaking the receiver violently and comminuting 



