C. Barus — Disti'ibution of Nuclei. 



181 



After 4 minutes (cf. fig. 3), the corona became spindle- 

 shaped, s = 5'4 cm in major axis, accompanied by rain from 

 horizontal layers of fog. 



After 6 minutes of exposure to the X-rays, the coronas 

 underwent remarkable distortion, becoming gourd-shaped (fig. 

 4), often with a long, serpentine neck, dipping into the B-side 

 of the condensation chamber. The length of figure on the 

 goniometer was about 6 # 8 cm , the outline being orange and the 

 field within greenish. Rain and fog abounded. The coronas 

 on second exhaustion (after adding filtered air) were g-b-p, 

 s = 4'9. n = 42000 and w-r-g, * = 4'5, n = 32000, on the A 

 and B sides respectively. The experiment was repeated with 

 like results. 



After 8 and 11 minutes of exposure, both the A- and B-side 

 became the seat of the now wedge-shaped corona (cf. fig. 5), 



greenish within and orange in outline. There was much rain 

 and fog. 



The figures, 1-5, are seen immediately after the exhaustion. 

 A moment later there is a storm-like disturbance in the con- 

 densation chamber, accompanied by rain and fog. Hence the 

 distribution of nuclei found on exhaustion is incompatible 

 with a persistent distribution of fog particles. In fact the 

 first coronas usually fall out rapidly, showing the occurrence 

 chiefly of large fog particles in spite of the horizontal extent 

 of the corona. The second coronas are circular and persistent, 

 whence a nearly uniform distribution of nuclei may be inferred. 



9. Symmetrically graded sizes or numbers of fog particles. — 

 Since the coronas obtained all show an unmistakable tendency 

 to horizontal symmetry with reference to the longitudinal axis 

 of the condensation chamber, the nuclei to which the coronas 

 are due must either originate in, or else be absorbed by, the top 

 and bottom of the apparatus. Nuclei originating or lost at the 

 front and rear faces are nearly uniformly distributed normal to 

 the line of sight and produce circular coronas. Nuclei origi- 



