414 Mr. C. V. Boys's Experiments 



will hang like a heavy drop ; then, on removing the finger, a 

 light may be put to the issuing vapour, which will burn like 

 a bunsen-burner. If, moreover, the bubble full of ether 

 vapour is held in a brilliant light, the shadow will show the 

 ether vapour oozing through the film and falling aw r ay in a 

 heavy stream (fig. 10). This experiment shows in succession 

 the floating of an air-bubble on a heavy vapour, rapid diffusion 

 of a soluble vapour through a soap-film, and the power of the 

 surface-tension to force the heavy vapour up a tube fast 

 enough to supply a large flame. 



Exp. 8. — Blow a bubble with oxygen gas in a jar partly 

 filled with ether vapour; on taking the bubble out of the vapour 

 and carrying it to a light, it will explode with a loud report. 

 Sufficient vapour will penetrate the bubble, even whilst it is 

 being blown, to make the mixture violently explosive. 



Exp. 9. — The w r eight of the air is well shown by blowing a 

 bubble with gas on a ring and then trying to blow an air- 

 bubble within it (fig. 11). The inner bubble is then pulled 

 out into a pear-shape, and very soon breaks away from the 

 pipe on account of its great weight. 



Exp. 10. — If Exp. 4 be repeated, but instead of a 

 heavy fixed ring a light aluminium one be used instead, to 

 which is tied a long piece of thread which may have a sheet 

 of paper at the end, then the whole combination will float 

 and rise in the air, even though, as in fig. 7, practically the 

 whole of the buoyancy is due to the gas in the inner bubble. 

 In this case the inner bubble is the bag of a balloon, the outer 

 bubble is the netting, and the wire and the things carried by 

 it are the car. In this case the power of the air-film to resist 

 contact of the two films is more evident than ever. If any 

 of the former figures 6, 7, or 8 are carrying a wire ring and 

 thread, as described, it is possible by a suitable pull at the 

 thread to release the pair of bubbles, which float away, one 

 inside the other, until the ceiling brings the experiment to 

 a conclusion. 



Exp. 11. — If the inner bubble of fig. 6 is made smaller 

 than the ring, then the corresponding experiment to that re- 

 presented in fig. 5 is shown in fig. 12. The small sphere will 

 always roll to the upper end of the outer bubble, which may 

 be pulled out to the cylindrical form and be inclined either 

 way. This modification of the other experiment was sug- 

 gested by Mr. Newth, to whom I had shown the previous 

 combinations. 



A great many experiments may be shown in which strings 

 of two or more bubbles, filled some with air and some with 

 gas, tend to pull in different directions. Thus an air-bubble 



