formed by Condensation at the Surface of a Solid. 523 

 Diameter of nucleus 260 x 10 -6 cm. 



Number of 

 exhaustions. 



Diameter of 

 water particle. 



Thickness of 

 film. 



1 



9 



280x10"!! 



310x10 : 



330x10 : 

 360x10"^ 

 390x10"^ 

 420x10 b 



10x10"!! 

 25x10 I 

 35x10 : 



50x10 : 



65x10 I 

 80x10 b 



3 



4 



5 



6 



Diameter of nucleus 360 x 10 -6 cm. 



1 



370X10 fi 



390x10 : 



410x10 I 

 420x10 : 

 440x10 I 

 460x10 b 



5x10 I 



15x10 : 



25x10 b 



30x10 : 



40xl0 _b 

 50xl0~ b 



2 



3 ...... 



4 



5 



6 





probably a very great pressure, in the liquid at the surface of 

 the solid. The author hopes to be able at some future time 

 to give the numerical values of this surface pressure for 

 various liquids in contact with glass. 



In now appears that in all cases where condensation of 

 moisture takes place at a solid surface, and at temperatures 

 not below the dew-point, the thickness of the surface film 

 varies from lOxlO"' 6 to 80 X 10~ 6 cm. according to the 

 substances used and the conditions of temperature and 

 pressure, and for the water film on glass in saturated vapour 

 at 15° C. the thickness is about 13'4 x 10~ 6 cm. 



According to Prof. J. J. Thomson * the mean radius of 

 the drops formed by condensation in electrified gas is of the 

 same order of magnitude, being 81 x 10 -6 cm. for negatively 

 electrified oxygen, and 68 X 10~ 6 cm. for positively electrified 

 oxygen ; the size of the nucleus is not known, but it is 

 probably very small. 



H.M. Dockyard School, Portsmouth. 

 November 1902. 



* J. J. Thomson, 'The Discharge of Electricity through Grasea ' (1900V 



