238 Dr. Rudorf on Latent Heat and Surface Energy. 



9. Again, with an induction coil, the line of demarcation 

 between the Faraday dark space and the positive column is 

 never well defined nor steady. This is in accordance with 

 theory, for owing to a rapid variation in the potential of the 

 induction coil, the energy of the field must vary in a rapid 

 manner. 



10. The peculiar behaviour of the stride indicates that they 

 are similar in character to the Faraday dark space and are 

 of similar origin. On the Quantum theory, accordingly, 

 they are regions over which the energy of discharge is 

 less than E . At very low pressure, before the disappear- 

 ance of the striae, both the Faraday dark space and the 

 strise continue to retain their breadth, showing that the 

 corresponding change of energy is negligible. 



XXIII. Latent Heat and Surface Energy. 

 To the Editors of the Philosophical Magazine. 



Gentlemen, — 



XN a recent number of the Phil. Mag. (vol. xxxviii. p. 240), 

 there appeared an interesting paper by D. L. Hammick 

 on a relation between the surface tension (7), the internal 

 latent heat (Li), the molecular diameter (<r), and the 

 molecular volume (V). For argon, the data used were 

 as follows : — 



7 =ll-00 dynes/cm. at T = 87° abs., L; =1284 cals., 



<r=3*21x 10~ 8 cm., d = M/V=l-404, 



whence 



J_I h- 996 --214 



the agreement between these two numbers being- considered 

 good. 



It does not appear to be generally known that the values 

 of 7 for liquid argon given by Baly and Donnan (Journ. 

 Chem. Soc. lxxxi. p. 907 (1902)) are incorrect. The correct 



