New Experiments with Soap Bubbles, 363 



surface, they can be detached from the pipe and started 

 floating. If the balance be well-adjusted, which is readily 

 accomplished by making the balloon a little smaller or larger, 

 according as the gas employed be strong or weak, it will hang, 

 like Mohammed's coffin, self- suspended in the air, if the latter 

 be quite still ; but being a very sensitive indicator of currents, 

 it will generally move in some particular direction. Thus it 

 will slowly creep along the walls of the room, mount to the 

 ceiling, and descend by the other branch of the current that 

 carried it up, or it will go so near the ceiling that its destruc- 

 tion appears inevitable. But not so; there being always a 

 cushion of motionless air on the surface of large objects, it will 

 float out of danger in a most surprising manner, unless some 

 asperity of surface should attack it. If it escape the latter 

 danger, it will remain floating and creeping about till it 

 gradually loses some of the coal-gas by solution in its liquid 

 sides, when, becoming heavier, it sinks and bursts. 



Notwithstanding the sensitiveness of our bubble to unkind 

 usage, it possesses in some respects a very remarkable invul- 

 nerability. It is well known that ghosts and other apparitions 

 do not sustain the least injury either when they are shot at, 

 chopped at with battle-axes, or pierced with sword thrusts — 

 in fact, this peculiarity is invariably demonstrated in perfect 

 ghost stories. This peculiarity is shared by the fairy-like sub- 

 ject of the present article. Pierced with needles, thrust at 

 with knitting-pins, they remain without a wound, nor does a 

 scar remain to testify the gash. Drops of water and small 

 shot may be sent through them without producing any percep- 

 tible symptom of inconvenience j indeed, they may be pierced 

 with a pen- knife (in a manner that would reduce a less eerie 

 thing into slices), with scarcely any disturbance of its unsub- 

 stantial being. But like the silver bullet which infallibly 

 destroys a ghost, so does a particle of grease on any of the 

 above offensive weapons destroy our bubble, for then it re- 

 quires but a single touch, and all is over— it vanishes; its 

 liquid sides can no longer adhere, as though its stainless 

 nature could not endure the impure contact. 



This property of invulnerability suggests, however, to the 

 unpoetical mind some curiosity as to the thickness of this 

 strange liquid film that forms our bubble. It certainly seems 

 at first almost impossible to effect a measurement of so intan- 

 gible a magnitude, and of a substance which cannot, from its 

 nature, be put (as in the case of gold leaf) into the balance and 

 weighed. It is true that there is furnished by the light which 

 produces such splendid tints on reflection from its two sur- 

 faces, an indirect means by which the distance that separates 

 them can be ascertained, supposing the angle of vision at 



