STANDARDIZATION AND EFFICIENCY OF THE FOG CHAMBER. 



39 



30. Results. The results are constructed in fig. 1 1 in comparison with 

 typical results for apparatus No. i. The same high efficiency already 

 recognized in case of this apparatus in table 13 is again exhibited, the 

 nucleation caught actually reaching over 4,000,000 per cubic centimeter 

 or invading the region of orange coronas, o t , of the first order. It is now 

 probable that with green monochromatic light the green corona, g t , of 

 the first order may actually be detected. With white light, however, the 

 initial effect is a mere fog. 



A number of trials with radium (I to V, within the chamber) exhibited 

 the same terminal coronas as in the fog chamber No. i . Ions are caught 

 with the same facility in both chambers and about at the same dpi p. 

 In other words, whereas vapor nuclei are caught in greater number by 

 the more efficient small fog chamber, this is not the case with ions, as 

 comparisons of the earlier records for No. i show, nor with the positions 

 of the fog limit and rain limit. Moreover, in series 5 and 6, obtained with 

 the excessively large apparatus, the ions are appreciably displaced after 

 condensation has begun, showing that the supersaturation is excessive. 



In series IV there is a pronounced decrease of the nucleation with 

 increasing dp I p. From the maximum n = 584,000 at dp/p = o.^i, the 

 nucleation drops uniformly to ^=416,000 at dp/p = o.$4. Inasmuch as 

 the correction for increased precipitation has been applied (smaller 

 coronas at high pressure-differences, because more water is precipitated), 

 this result is to be associated with the greater removal of nuclei at high 

 exhaustion. The coronas show the number of nuclei in the exhausted 

 fog chamber. 



The smaller nucleations in series V and VI are referable in part to 

 the weaker radium used and in part to the exceptionally large vessel 

 employed. 



31. Conclusion. The final question of interest is a revised comparison 

 of these results with C. T. R. Wilson's disk colors, if his two extreme 

 greens are interpreted as g 2 and gj instead of g 3 and g 2 , as preferred in the 

 preceding report.* In such a case the nucleations may be estimated as 

 follows: 



*Am. Jour. Sci., xxiv, 1907, p. 309; Carnegie Institution of Washington Publication 

 No. 96, 1908, sec. 35. 



