AIR ENERGIZED BY X-RAYS. 



43 



The following fog limits were made out with the aid of the same 

 fog chamber of waxed wood, used above : 



A few other cases will be added below, giving for stronger radiation 

 at a distance of 2 cm. and for only 2-minute exposure fog limits at 

 5 and 4 cm. In each case the air was rigorously freed from dust by 

 filtration before the exposure began. Hence the nuclei are due to 

 the X-rays alone, and their size increases indefinitely with the intensity 

 of the ionized field. Indeed as to size they eventually in no wise differ 

 from phosphorus or other efficient nuclei, and require almost no super- 

 saturation to induce condensation. 



24 .28 S. 3fi 



10 



12. 



16 is w 



FIGS. 38-39. Apertures (s) and nucleations () varying with the pressure differences 

 (5/>) for the case of persistent nuclei produced in dust-free air by the X-rays. 



Table 17, referred to iii figs. 38 and 39, will be found as table 27, p. 45. 



39. Sudden exhaustion in the absence of condensation. in many of 

 the experiments the nuclei seemed to be destroyed by sudden exhaus- 

 tion even when no condensation took place, the pressure differences 

 lying below the fog limit. As this is an important question bearing 

 on the flying to pieces of the nucleus, special investigations were made 

 as detailed in the following tables. The point at issue may be stated 



