24 On the Motion of Fluid Bubbles through Liquids. [June 1, 



experimentally unverified factor in our expression for the velocity of 

 the bubble. That is to say to verify the terms under which the 

 acceleration (g) appears in the expression. This, were it desirable, 

 might of course be investigated by an arrangement utilising centri- 

 fugal force, but without elaborate arrangements it is nofc difficult to 

 observe the great influence increase in pressure produced by swing- 

 ing a tube round and round by hand has. To take an example, a 

 bubble of creasote in a tube of glycerine of diameter = 0'31 takes 

 over 13 hours to travel 1 m. By swinging it round and round in the 

 hand, one can get it through in less than as many minutes. 



In connection with this the comparative ease with which a stray 

 liquid bubble in the tube of a thermometer can be brought home by 

 swinging in the hand will suggest itself. 



PART II. 



When the length of the bubble is less than a certain thing, the 

 velocity is found to be very different for different sized bubbles. The 

 result of some experiments made with different sized bubbles of air 

 passed up through a tube of water of diameter 0'665 is exhibited in 

 Diagram III. 



The ordinates represent the velocity and the abscissae the volume 

 of the bubble measured in terms of the length of tube it occupies 

 when at rest. The length of the bubble in motion is always of course 

 greater than this. 



It will be seen that the velocity corresponding to a, volume of about 

 7 is nearly double that at about 5-5. The phenomenon is, doubtless, 



