182 0. Bar us — Distribution of Nuclei. 



nating or lost at the left hand end of the chamber will addi- 

 tionally distort the corona, and such distortion is in evidence. 



Mere inspection of the coronas, 1-5, shows that they are 

 larger for fog particles near the axis, and smaller for particles 

 near the top and bottom of the condensation chamber. Hence 

 it is next necessary to explain that the details of the distorted 

 coronas observed actually correspond with a gradation of the 

 number of effective or available nuclei, from the axis outward 

 on all sides. In the case of linearly graded fog particles 

 increasing in diameter, 8, from bottom to top (A), it appears 

 that the equation of the apertures, s, of the loci* of like color 

 of the coronas is 



a sm <f> \ 



where s is the aperture of the particles of diameter, S in the 

 horizon or plane of sight, and $ the angle in polar coordinates 

 between the radius vector to the part of the corona in ques- 

 tion and the horizontal, the origin being at the center of the 

 corona. Finally 8 = S — ah, where 2A = s sin <fi. Such coronas 

 when the gradation becomes marked are camjpanulate in out- 

 line, finally becoming basin-shaped. 



In the present case, however, there are two symmetrical dis- 

 tributions of this kind, i. e., increasing diameters of fog par- 

 ticles from the axis of the chamber towards the top and the 

 bottom. Hence pairs of intersecting curves, two examples of 

 which are given in figure 6 («'>#), show the coronas to be 

 anticipated, if the remote parts beyond b and c of the corona 

 are ignored, as they have no bearing on the symmetrical case, 

 and only the curves surrounding the spot of light, d, admitted. 

 In other words, as the distance he, varying with the number of 

 axial nuclei and the distribution constant a, increase, all the 

 figures 1, 2, 3, 4, 5, may be logically evolved. 



On the left end face, moreover, there would be special inter- 

 ference with the distribution of nuclei giving rise to the corre- 

 sponding distortion seen in the coronas. Further distortion 

 due to the decrease from left to right of the intensity of the 

 radiation must also be apparent, and the gradient of distribu- 

 tion will be slightly altered by diffusion. One may note that 

 if anything issues from the walls of the vessel, it comes as 

 abundantly out of the water below as out of the wet cloth 

 above. 



10. Origin of nuclei at the walls of the receiver. — As has 

 already been suggested, the observed gradation of fog particles 

 may result from the (real or virtual) evolution of effective 

 nuclei at the top and the bottom of the apparatus, in conse- 



* Barus : this Journal (4), xiii, p. 309, 1902. 



