DISTRIBUTIONS OF NUCLEI. 73 



52. Discussion. The new curves (fig. 33) lie nearer together for the 

 energized and non-energized states of the gas. This obviously results 

 from the correction applied to the observed values of dp. Neither do 

 the graphs ascend as highly as they did before, for the same reason, 

 remembering that the nucleation (n) always refers to the exhausted fog 

 chamber. Again, the new curves must be steeper than the old; but both 

 of them, i.e., the curves for the non-energized and for the energized 

 gas, have about the same slope, so far as can be made out for the case 

 of such steep curves as those under consideration. Nevertheless, it is 

 probable that there is some other reason implied in this, which is yet 

 to be made out. For the ionized state the observations frequently 

 suggest a kind of saturation beyond which the ions pass into per- 

 sistent nuclei very much as a vapor condenses. In other words, a 

 maximum ionization pressure, determined by a definite number of ions 

 per cubic centimeter, which can be approached as the radiation is 

 more and more intense, but not exceeded, is a useful conception in con- 

 nection with many of the experiments given. 



53. Summary. The general summary of this chapter has already been 

 given in sections 42, 43, and 52, particularly in the former, with regard to 

 fig. 25, and need not, therefore, be repeated here. The highest order of 

 available coronas has been invaded and surpassed. 



It appears that the limits of efficiency of the practical fog chamber 

 with rapidly opened plug cock have been reached when the long cylin- 

 drical vessel of about 6,000 c. cm. is exhausted into a vacuum chamber of 

 about 100,000 c. cm. through a pipe not less than 5 cm. in bore nor more 

 than 50 cm. long, with a stopcock of wider diameter (7 to 8 cm.) inter- 

 posed. To test this again, such a fog chamber was adjusted as shown in 

 fig- 34 (V vacuum chamber; F fog chamber; G, g, gages at the former 

 and the latter, the whole mounted on casters to admit of shaking the 

 water in F; goniometer attached to fog chamber). The results are given, 

 both for fog chambers Nos. I and II, in tables 24 and 25, with correc- 

 tions for the barometer as explained in Chapter VI, sections 100 and 101, 

 and they are charted on a small scale with other data (table 23) in 



fig- 35- 



The graph for chamber number II would coincide with data inferred 

 from Wilson's colors for small coronas; but for large coronas it actually 

 lies in a region of lower exhaustion to which however, too much 

 importance must not be attached, because of the difficulty of identifi- 

 cation. The point is that the apparatus of 2 -inch pipes is quite the equal, 

 if not the superior, of the apparatus with 4-inch pipes, in the region of 

 both the lower and higher coronas. Curiously enough, the apparatus I 



