6 



VAPOR NUCLEI AND IONS. 



present, showing that the result is not incidental. As both ends of the 

 chamber were about equidistant from the radium, it would appear to be 

 the excess of the secondary radiation from the metal cap which is in 

 question. 



Table 2. Distribution of nucleation within the glass fog chamber (as in table 1) 



and allied results. 



1 Three hours later no interference. 



wrg. 



5. The same, continued. X=rays. After finding that the fleeting 

 nucleation within the fog chamber was unequally distributed under the 

 excitation of radium, similar experiments were tried with the X-rays, 

 using the fog chamber (fig. 4) with four horizontal wet cloth partitions 

 2 to 3 cm. apart to obviate convection. The results given in the first 

 part of the following table are definitely affirmative. When the X-ray 

 bulb is near the fog chamber, the nucleation nearer the bulb is decidedly 

 in excess. Thus when the line of sight is 30 and 50 cm. from the anti- 

 cathode, the farther nucleation is about 60 per cent of the nearer. 



If, however, the bulb is relatively far away (D = ioo or 200 cm.), the 

 end of the fog chamber farthest from the bulb and near the brass cap is 

 more actively ionized. In other words, under these circumstances the 

 secondary radiation from the brass cap predominates. The nucleation 

 at 10 and 30 cm. from the latter shows a decrement of 20 per cent, for 



