208 C. Barus — Changes of Colloidal JSTucleation. 



8. Effect of ionization. — To find whether there is any rela- 

 tion of the change of nncleation in the fog chamber in the 

 lapse of time with a state of ionization of the atmosphere, 

 measurements were made of the latter quantity by Miss L. B. 

 Joslin, using Ebert's aspirator apparatus. 



These data are constructed in the lower curves of figure 2 

 together with the cotemporaneous nucleations and tempera- 

 tures of the fog chamber. It would be difficult to detect any 

 detailed similarity in the two sets of results. Thus the maxi- 

 mum of nucleation on September 20 to 24 is in no way sug- 

 gested by the ionization. 



9. Mean results. — The most satisfactory criterion of the 

 variation of n 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 = (Sj) — (ir — ir^/ip — tt) : but as these 

 points lie on a graph whose curvature is often marked, the 

 curvature would in general be hard to estimate and the ordi- 

 nate n 3 35 for cc=*335 has therefore been preferred. 



The endeavor may be made to test the average value of 

 ^. 333 for longer intervals of time. As the series is often inter- 

 rupted, two to four-day intervals suggest themselves. Conse- 

 quently if the data be so compared the following values appear. 

 If the results of the table are to be further corrected for the 



Nucleations (arei 



•aged in groups of 



2 to 4 days) 



in the lapse 



of time. 



August 







to October, 



1906. See fig. 3. 















Positive 



Negative 







Corrected 



Temp- 





Ionization 



Date ii. S3 



sxlO- 



3 51.335 x 10~ 



3 erature 

 °C. 



Barometer 

 cm. 



n x 10- 3 



n x 10- 3 



Aug. 10-13 



77 



87 



25-8 



75-71 







. - . 



14-17 



72 



78 



23-8 



•71 











23-26 



73 



79 



23-6 



76-07 



. 



. . . 



27-29 



68 



74 



23-8 



75-50 











Sept. 7-10 



57 



60 



22-3 



•44 



• . - 







11-13 



56 



59 



22-0 



•98 











14-16 



47 



49 



21-2 



76-47 



1-60 



1-57 



17-20 



45 



47 



21-6 



•08 



1-09 



•90 



21-23 



75 



79 



22*5 



75-72 



•97 



1-55 



24-27 



37 



37 



196 



76-63 



1-00 



•79 



28-30 



37 



37 



19-0 



•37 



•88 



1-23 



Oct. 1-3 



32 



30 



180 



•10 



1-04 



1-11 



4-5 



44 



45 



20-8 



75-75 



1-17 



•40 



6-7 



40 



41 



20-6 



74-85 



•76 



•47 



8-9 



36 



36 



20-3 



76-08 



1-22 



•92 



10-11 



35 



35 



19-7 



75-17 



1-26 



•64 



12-13 



27 



27 



18-7 



76-97 



•96 



1-22 



14-15 



40 



40 



20-2 



76-90 



1-57 



•40 



