DECAY CONSTANTS PERSISTENT NUCLEI. 



57 



If N be expressed in thousands per cubic centimeter, the following 

 is a summary of the results obtained : 



The effect of periodicity is still in evidence, seeing that the large 

 coronas are apt to be followed by relatively small coronas. Some 

 special results are given in the table. The coronas at these distances 

 are round, but blurred, showing the occurrence of nuclei of all sizes. 



At D 40 cm. (table 33 and curve 48), the results are not essentially 

 different. The X-ray bulb is weak at first, but seems to recuperate in 

 the course of the work . In other respects the two curves are essentially 

 the same, as the above data show. In spite of the variability of the 

 X-ray bulb, the insignificant differences of nucleation in these two 

 cases are astonishing, for the distances vary from 40 to 150 cm. The 

 law of inverse squares would predicate a fourteen -fold decrease. In 

 fact, the same anomalous result seems to hold quite up to the fog cham- 

 ber, as suggested in the data of table 34. 



The bulb in table 34 is unfortunately weaker, showing only about 

 half the nucleation of the preceding case (^ = 48,000 at 8p = 24.8 cm., 

 for instance) in spite of greater nearness (Z?=iocm.). The earlier 

 data may have been larger, ^-=63,000 being among these. The fog 

 limit has been definitely reduced from 20 cm. to 18 cm. 



Generation is now no longer instantaneous ; certainly not at 

 8p = 20. i , though the data at the larger pressure difference 8p = 25 are 

 not decisive. It takes at least 2 minutes for the given radiation to 

 saturate the air with nuclei corresponding to 8p = 20. i . (See curve 51.) 



In conformity with the slow generation of nuclei the period of decay 

 is now definitely prolonged. In 3 to 4 minutes the nucleation is 

 reduced one-half. 



48. Persistent nuclei. The data for stronger radiation, showing 

 remarkably persistent nuclei by comparison, have already been given 

 in Chapter II, section 37 et seq., and are repeated in the annexed 

 curve (50). Roughly, the reduction is one-half in about 10 minutes 

 and four-fifths in 80 minutes, contrasting sharply with the reductions in 

 2 seconds and 20 seconds, respectively, in the case of weak ionization. 



