TIME VARIATIONS OF NUCLEI. 



161 



Fig. 65. Independent fog chambers with 2-inch and 4-inch efflux side by side. 

 Vacuum chambers, V and V ; fog chambers, F and F'. 



finally selected. At the outset the values of 5 may be uncertain, because 

 of internal sources of nucleation and similar difficulties. 



Four observations were usually made daily. Data corresponding to 

 I and II are distinguished by subscripts, and those of II were usually 

 observed about five minutes after the time given for I. One may note 

 the much greater efficiency of the apparatus with 2-inch pipes as com- 

 pared with the other with 4-inch pipes, the reason for which is not easily 

 seen. As a whole the observations for apparatus I during the end of 

 June and the beginning of July run parallel to the barometric decrement, 

 and the astonishingly high values on June 29 and 30 occur during a period 



Tablb 55. Colloidal nucleations near the fog limit in their time variations. Fog cham- 

 ber I with 4-inch exhaust pipes; dp = p - p 3 =27 cm.; II with 2-inch exhaust pipes; 

 dp = p- 3 = 25.6 cm.; p-p 2 = 21 cm. and 20 cm., respectively. 



1 Early results. 



2 Results in succession. 



