42 CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



For the same reason would it be unwarrantable to look for effects 

 due to variations of any external radiations. In other words, it is 

 improbable that Wood and Campbell's phenomena can be detected by the 

 fog chamber, and the results which seemed at first in accord with it 

 are due to a rise of temperature. The results show that dp/p is a suitable 

 variable for the comparisons of nucleations in a plug-cock fog chamber 

 like the above. 



Finally the temperature conditions within the fog chamber produce 

 a very definite effect, amounting to an increase (cceteris par-ibus) of 

 about 2000 available vapor nuclei per degree centigrade near 20 and 

 the given exhaustion /> 7^ = 0.345 or v 1 /v = i . 35. Estimating the average 

 number of efficient nuclei present at 25,000, this amounts to an incre- 

 ment of about 8 per cent per degree. Anomalous as it may seem that 

 rise of temperature should increase the number of efficient nuclei (ccet. 

 par.}, probably by increasing their size throughout, nothing has been 

 suggested to explain this result away. Virtually the same thing is done 

 by radiation, though in much more marked degree than by temperature, 

 so that one might regard ionization as a state of dissociation sufficiently 

 advanced to set free corpuscles, or equivalent to a high degree of 

 temperature. One might therefore expect a passage of the vapor nuclei 

 of wet dust-free air into the ions, through a continuous gradation of 

 nuclei; and in fact (granting that other valid explanations for the 

 occurrence of ions have been given) , they always occur together. 



The present and a variety of other results made it necessary to re- 

 standardize the coronas in terms of the number of nuclei represented, 

 and the work will be given in the next chapter. Some of these data 

 have already been utilized in the above. 



