36 CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



19. Mean results. The most satisfactory criterion of the variation of 

 nucleation in the lapse of time would perhaps have been the slope of the 

 n lines as given by the three observations in terms of the abscissa, 

 x=(3p [n 7Ti])/(/> ?r); but as these points lie on a graph whose 

 curvature is often marked, the curvature would in general be hard to 

 estimate and the ordinate .335 f r :V = -335 ^ as therefore been pre- 

 ferred and is summarized in table 13. 



TABLE 13. Summary of table 9. Observations a. m. and p. m. 



>-TT) = 0.335. 



The endeavor may be made to test the value of 0-335 for longer inter- 

 vals of time. As the series is often interrupted, 2-day to 4-day intervals 

 for the present suggest themselves. Consequently, if the data of table 

 13 (which is a summary of table n) be so compared, the values given in 

 table 14 appear. 



If the results of table 13 be further corrected for dependence of the 

 precipitation on the changes of temperature of the fog chamber, data 

 given in an earlier report* and elsewhere are available. 



At dp = 22 cm. the amount of water precipitated per cubic centi- 

 meter is at 



/= 10 20 30 



wXio"= 4.2 5.5 6.7 



Hence on the average the correction may be taken as ^ -==2.3 per 



5-5 X 20 



cent of the values of m at 20 C. 



*Smithsonian Contributions No. 1651, p. 135, 1905. 



