1903.] on Drops and Surface Tension. 289 



them together to one side of the vessel ; but there was a resistance if 

 they were so numerous as completely to cover the mercury surface, 

 and if on being pushed together they had to mount one on top of the 

 other. 



Finally, Lord Rayleigh showed his audience the effect of dirt 

 or grease in the liberation of gas from champagne or soda-water. 

 The adherence of the bubbles, he was sorry to tell them, was a sign 

 of the dirtiness of the glass, as he showed by putting in soda-water 

 two iron reds, one treated so as to be free from grease and the other 

 not, when the bubbles were seen adhering to the latter, but not to 

 the former. 



