DISTRIBUTIONS OF NUCLEI. 



45 



series, with the window open (tin plate removed), the last series being 

 a detail for the initial part of the curve, which is of especial interest. 

 The results are also shown in fig. 24, where their relation to the lowest 

 curve, J9 = 6oo cm., for the open or non-inclosed X-ray bulb becomes 

 evident. In each of these curves there is a definite horizontal branch 

 within which the ions predominate. Beyond this lies the rise due to the 

 colloidal nuclei, but the curves, and particularly the asymptotes, are 

 depressed in both cases. 



Table 16. Nucleations at different exhaustions. 2^-inch cock, 2-inch piping, 12 

 inches long. X-ray bulb in lead case at D = 6oo cm. from glass fog chamber. 

 Aperture in case 7.5 cm. in diameter. 



1 Open side over i foot square. 



2 Lead sheet 0.12 cm. thick; tin plate 0.03 cm. thick. 



3 After long waiting. 



42. Discussion. It will now be in place to make a more complete 

 survey of the manifestations of nucleation in dust-free air under any 

 conditions. Figs. 24 and 25 are useful for this purpose. With regard 

 to the method I may recall that the difficulties were enhanced by the 

 need of providing rapid exhaustions in case of a fog chamber large 

 enough to measure the coronas and to show the sequence of axial colors. 



