l8 CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



TABLE 7. Observations for axial color. Dust-free air, vapor nuclei, and ions. Long 



brass tube, 5 cm. diameter, 200 cm. long. 



*Fog limits. fDense but no color. JDense fog but no color. 



The same is true of phosphorus nuclei put into the identical (now cloth- 

 lined) apparatus. Thus in case of long brass tubes 200 cm. in length and 

 5 cm. in diameter with the barometer at 77.15 cm. at 20, thirteen succes- 

 sive exhaustions of air charged with phosphorus nuclei showed no color 

 effects, but merely fogs gradually decreasing in density. The drop of 

 pressure lay between 10 and 16 cm. 



Again, four exhaustions with fresh charges of phosphorus nuclei be- 

 haved similarly. The nucleated air was usually fawn-colored by trans- 

 mitted light and bluish by reflected light. Finally, when many successive 

 charges of phosphorus nuclei were introduced, densely black fogs appeared 

 without color, gradually lifting. 



