New Experiments with Soap Bubbles. 



365 



has been obtained of a thickness not exceeding one two-mil- 

 lionth of an inch, while gold leaf itself is exceeded slightly by 

 the thinness of the film of the black spot I have described as 

 being formed on the upper pole of an undisturbed bubble, 

 which has probably a thickness even less than three eight- 

 millionths of an inch. When we consider that this film yet 

 contains only about a fiftieth of its weight of soap, a substance 

 of highly complex atomic constitution, we obtain some notion 

 of the almost infinite divisibility of matter. 



Thin as is the film that forms our bubbles, yet its equality 

 of tension is such, that by dexterous management they may be 



blown to a giant size. For this purpose the tobacco-pipe 

 must be discarded, as it neither gives a large enough film to 

 commence with nor supplies air with sufficient rapidity. A 

 small glass funnel, of about 1-f- in. in diameter, cemented by 

 some marine glue, with its mouth downwards, into a glass tube 

 connected with a double-action bellows, must be employed. 

 The connection between the tube and bellows should be made 

 with a caoutchouc tube, and supplied with a stop-cock or clamp 

 for regulating the supply of air. A small flat basin, containing 

 some of the bubble solution, should be employed to form a 

 film across the mouth of the funnel, which is then expanded by 

 careful supplies of air from the bellows. When the bubble has 



