20 



VAPOR NUCLEI AND IONS. 



distorted coronas. These data are constructed in fig. 18, the s values 

 being dotted and the N values drawn in full. 



140 



i?o 



'00 



300 



350 



ZOO 



Fig. 17. Nucleation (A/) for different exhaustions (dp) and radiations. 



Bulb distance. 

 Fig. 18. Persistent nucleation (A/) produced by X-rays acting from 



different distances (D) from the glass fog chamber. Table 9. 



15. Persistent nuclei generated through tin plate. In view of the 

 ease with which the cylindrical fog chambers may be made rigorously 

 air-tight, it seemed worth while to endeavor to produce persistent 

 nuclei through a plate of tinned sheet-iron, 0.03 cm. thick and 14 by 

 20 inches square. In the following trials exposures for 2 minutes to the 



