58 NUCLEATION OF THE UNCONTAMINATED ATMOSPHERE. 

 TABLE 35. Data for persistent nuclei. D = 6 cm. 



* Distorted. 



Assuming the above equation ilN=a-\-bt, or dN\dt = bN*, for 

 which, however, there is no immediate justification here and which 

 does not fit well, values of the order of a = o.oi and b = o.ooooi follow. 

 The decay is thus shown to be several hundred times slower than 

 above, under like assumptions. 



In table 36 and curve 51 specific results for the generation and decay 

 of nuclei have been added, obtained with a bulb strong at first, but 

 eventually losing intensity below the necessary limit. The first part 

 of the table shows a law of generation increasing with the time of 

 exposure at an accelerated rate, consistently throughout the 180 sec- 

 onds of observation. The remaining conditions have already been 

 investigated in Chapter I. Measurement is difficult because of the 

 distorted coronas, which soon become densely stratified fogs. The 

 pressure difference used (ftp = 20 cm.) is below the fog limit for air. 



The curve (51) for nucleation (A^) shows an enormously rapid 

 increase after i minute of exposure, as though the nuclei themselves 

 became radio-active, temporarily. This increase is sustained even if 

 the radiation is cut off. (Section 56.) 



The results for decay, in case of the persistent nuclei here obtained, 

 are complicated and must be given in curves. In the second part of 

 the table the minute exposures show but slight, if any, decay, in the 

 absence of radiation, after the lapse of i minute. The 2-minute 

 exposures actually seem to show increased nucleation in the minute 

 succeeding exposure (secondary radiation, section 16); but in the 

 ensuing 5 minutes after radiation, decay is manifest (curve 51). The 

 behavior of the fatigued X-ray bulb may be contrasted with this, in 

 the same position (part IV). The nuclei vanish as in the third part 

 of the table, in spite of the 2-niinute exposures as compared with the 



