[907 ] 



BARUS— NUCLEI IN DUST-FREE WET AIR. 



75 



nr* 



Figs. 4 and 5. Results essentially like the cases of figures 2 and 3 l^"t 

 obtained by the method of two sources. The scale of nucleation is more 

 compressed (ordinates nXio"'). X, R, A, show the points at which con- 

 densation on ion.s produced by strong X-rays, by radium, and by natural 

 radiation (dust free air) were observed. W refers to Wilson's results. Fig- 

 ure 5 is an enlargement of figure 4 in the region of ions or for low values 

 of 5/7//). T shows the results of J. J. Thomson. 



