326 Lord Rayleigh : Investigations in Capillarity. 



motion which occurs during the sepai*ation of the drop that 

 could be influenced. When the diameter is moderate, the 

 most rapid motions occur at a level considerably below the 

 tube, and the obstruction presented by the flat face of a 

 thick-walled tube is unimportant. 



The observations give materials for the determination of 

 the function F in (1). In the following table, applicable to 

 thin-walled tubes, the first column gives values of T/gaa 2 , 

 and the second column those of #M/Ta, all the quantities con- 

 cerned being in c.G.s. measure, or other consistent system. 



T/gaa 2 . 



</M/TV. 



258 



4-13 



116 



3-97 



•703 



3-80 



•441 



3-73 



•277 



3-78 



•220 



3-90 



•169 



4-06 



From this the weight of a drop of any liquid of which the 

 density and the surface-tension are known can be calculated. 

 For many purposes it may suffice to treat F as constant, 

 say 3"8. The formula for the weight of a drop is then simply 



Mg = 3STa, (2) 



in which 3'8 replaces the 27r of the faulty theory alluded to 

 earlier. 



The Liberation of Gas from Supersaturated Solutions. 



The formation of bubbles upon the sides of a vessel con- 

 taining " soda-water" or a gas-free liquid heated above its 

 boiling-point, is a subject upon which there has been much 

 difference of opinion. In one view, ably advocated by Gernez, 

 the nucleus is invariably gaseous. That a small volume of 

 gas, visible or invisible, provided that its dimensions exceed 

 molecular distances, must act in this way is certain, and the 

 activity cf porous solids is thus naturally and easily explained. 

 But Geruez goes much further, and holds that the activity of 

 glass or metal rods, immersed in the liquid without precaution, 

 is of the same nature, and to be attributed to the film of air 

 which all bodies acquire when left for some time in contact 



