4o 



VAPOR NUCLEI AND IONS. 



Several interesting features are seen in the radium and X-ray curves in 

 fig. 23, to which special attention may be called. It will be observed that 

 the curves for distances D = io and 20 cm. of the anticathode from the 

 sides of the fog chamber begin and terminate in nearly coincident curves 

 and coronas, but that they lie at some distance apart in their middle 

 regions. Hence available* nuclei are apparently not more numerous 

 eventually in one case than in the other, but they are larger (virtually) 

 in the middle regions for the stronger radiations; in other words, the 

 asymptote is more quickly approached for the stronger radiation. 



500 



400 



300 



100 



100 



Fig. 23. Efficient nucleations (n) in dust-free air, energized or not, as specified 

 at different exhaustions (dp). Table 14. 



Again, the terminal corona in case of the data for X-rays is reached long 

 after the final coronas for the weak radiation from radium (10 mg. 

 io.oooX); i.e., the number of nuclei (ions) in the case of the weak 

 radiation ceases to increase in a region of lower exhaustion, apparently, 

 than the one observed for the more intense radiation. Hence in case of 

 the'latter, finer gradations of nuclei appear to occur, as if the radiation 

 shattered certain of the larger ions. There is, however, another point of 



*It will appear below that for nuclei, large or small, the limit is reached with the 

 given number of nuclei per cubic centimeter, corresponding to the gBP corona. Nuclei 

 in excess of this, large or small, are inefficient. 



