No. 30. — X-ray 

 nuclei. Scale 

 part, .0030 cm. 

 Fall 45 sec. 



No. 10. — Air nu- 

 clei. Scale part. 

 .0012 cm. Fall 

 30 sec. 



No. 25. — X-ray 

 nuclei. Scale 

 part, .0030 cm. 

 Fall 30 sec. 



No. 27. — X-i 

 nuclei. Sc 

 part, .0030 c 

 Fall 15 sec. D 

 in negative. 



No. 23.— X-:V 

 nuclei. Seal 

 part, .0030 

 Fall 30 sec. 



No. 9. — P nuc 

 Scale part, .0 

 cm. Fall 4 

 sec. 



No. 4. — P nuclei. 

 Scale part, .0044 

 cm. Fall 20 sec. 



Figure 10. — Micro-photographs of Fog Particles, Precipitated on Persistent Nuclei usually 



Produced by the X-rays in Dust-free Air. 



116 



