GENERATION AND DECAY. 



55 



Data are given in table 32 et seg., the pressure difference being 

 chosen at the fog limit of dust-free air, which under these conditions 

 contributes but a few per cent of the nuclei. The first part of table 

 32 shows that the origin of nuclei is practically instantaneous. Within 

 5 seconds after the radiation from the X-ray bulb (placed at D = i^o 

 cm.) begins, the air within the fog chamber is saturated with nuclei 

 (curve 47). 



Decay is not quite instantaneous, but enormously rapid as compared 

 with the care for intense radiation of the preceding chapter. The 

 number of nuclei per cubic centimeter is reduced one-half in about 

 2 seconds and reduced one-fifth in 20 seconds. After 120 seconds the 

 nucleation of dust-free air is practically regained. The decay is not 

 apparently exponential in character. If A r =A r e"at ) t jj e <jata o f 

 tables 32 and 33 are badly reproduced. With N=N l(i-\-b'f) or 

 ilN=a-\-bt, the agreement is as good as the observations. Hence 

 dn\dt = bn*, or the decay is as the square of the number, showing that 

 the destruction is mutual between the nuclei as if they were positive 

 and negative ions. 



TABLE 32. Generation and decay of the nuclei. X-radiation, bulb at D = 150 cm. 

 5^ = 25 cm. Filter and wet-sponge tube. 



* Dust-free air not energized. 



\ Note the low apertures after full corona. 



\ Nucleation produced instantly. 



