CHANGE OF VAPOR NUCLEATION IN LAPSE OF TIME. 



exhaustion with fog and vacuum chamber in communication, all at the 

 same temperature; s is the angular diameter of the corona on a radius 

 of 30 cm., when the source of light and the eye are at 30 cm. and at 

 250 cm. on opposite sides of the fog chamber. Finally, n shows the 

 number of nuclei per cubic centimeter. 



TABLE 6. Time variation of the larger colloidal nucleation of dust-free air. Conical 

 filter, dp readjusted. App. I, 4-inch pipes; app. II, 2-inch pipes. 



While the data for apparatus I still recall the barometer graph, this 

 is not the case for apparatus II, and neither of the graphs I or II are 

 as strikingly suggestive of the variations of atmospheric pressure as 

 was the case in the earlier report. The discrepancy in the new results 

 may be an overcompensation, although all the details of the experi- 

 ments themselves were gradually more and more fully perfected; or 

 the rise in the region of ions may just balance the decrease of the num- 

 ber of efficient colloidal nuclei due to the increase of the former. In 

 fact the region where ions predominate may rise while the regions where 

 the vapor nuclei are more important may correspondingly decrease, 

 producing a diminished slope of the initial part of the graph such as is 

 often actually observed. It is necessary, therefore, to inquire somewhat 

 more carefully into the errors involved, to investigate some datum or 

 invariant which if kept constant will mean a corona of fixed aperture 

 in the given apparatus, unless there is actual radiation in varying 

 amount entering from without. 



