CHAPTER III. 



MISCELLANEOUS EXPERIMENTS. 



54. Objects. Having perfected the coronal fog chamber to the degree 

 specified in the earlier sections of Chapter II, it seemed expedient to make 

 use of it for a variety of purposes partly corroborating and interpreting 

 my earlier work, partly introducing new results. In particular, the growth 

 of persistent nuclei in a highly ionized medium in the lapse of seconds, 

 the occurrence of solutional nuclei, and like questions may be studied 

 by the depression of the terminal asymptote produced by the introduction 

 of relatively small numbers of larger nuclei into the medium. Again, the 

 effects of radiation from different distances on the medium of the fog 

 chamber, the absorption of such radiations, the distributions within the 

 fog chamber, etc., may be elucidated by this treatment. Finally, some 

 consideration of the rates of generation and decay of ions is in place and 

 a method will be shown for the standardization of coronas. Some final 

 remarks will be made on the steam jet and on the relation of its color 

 phenomena to those of the fog chamber. 



Throughout this chapter dp refers to the drop of pressure observed at 

 the isolated fog chamber under isothermal conditions, the exhaust cock 

 being closed as soon as possible after the expansion. The necessary 

 reductions (should they be needed) may be made as shown in the pre- 

 ceding section. 



55. Growth of persistent nuclei. In table 26 (illustrated by fig. 36) 

 the time during which the fog chamber was exposed to the X-rays, with 

 the anticathode at a distance of D = io cm. from the fog chamber, is 

 given in the first column. The coronas and the number (n) of nuclei 

 per cubic centimeter follow. 



The two series of experiments made show that there is a gradual 

 increase of the number of persistent nuclei, evidenced by the gradual 

 reduction of the number of efficient nuclei. In less than two minutes, 

 however, the phenomenon becomes more stationary, indicating that the 

 full number of persistent nuclei is being approached, or that there are 

 now about as many made as are unmade per second. It is difficult to 

 follow the phenomenon beyond this, for the coronas now become cam- 

 panulate or otherwise distorted, appearing in association with heavy 

 fogs. The true asymptote is probably far off. These data furnished 

 good illustrations bearing on the remarks of section 42, Chapter II. 



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