358 New Experiments with Soajp Bubbles. 



NEW EXPEKIMENTS WITH SOAP BUBBLES. 



BY JOHN BEOUGHTONj B.SC. 



Our subject is not of very difficult or complex manufacture. 

 It is very easy to take a little soap, and shake it up with, some 

 soft water in order to form a lather, to take a tobacco pipe and 

 dip it in the solution, and then the foundation of the bubble is 

 made. For across the bowl of the pipe the soap, dissolved 

 by the action of a cause of whose nature we know but little, 

 has enabled the water to form a film, which, liquid though it 

 be, is braced with a drum-like tension. This strain, whose 

 existence can be readily demonstrated, would, if the soap were 

 not present in sufficient quantity, cause the film to break im- 

 mediately by its own contractility. Now blow through the 

 pipe, and the liquid membrane will be swelled out, its capacity 

 for expansion far exceeding caoutchouc, and the thing of 

 beauty grows rapidly to its maturity, and glows with all the 

 magnificence of its perfections of colour and form, changing 

 every second in the former, until the limit of its strength 

 being reached, fragile as lovely, it vanishes into invisible spray, 

 leaving its name as a byword for beauty without substantiality. 

 To make evident this contractile force of the film, which is at 

 once the cause of its existence and destruction, it is only neces- 

 sary to blow a bubble with a moderately wide glass tube 

 instead of a tobacco-pipe, and when it has attained to con- 

 siderable dimensions, to present the end of the tube to the 

 flame of a lighted candle, when the contractility of the film 

 will expel the contained air with such force as to extinguish 

 the candle. If, instead of expanding the bubble to its limit 

 of strain it be dexterously jerked off its parent pipe, by virtue 

 of the same cohesive force it instantaneously closes the rent 

 made in its side and floats a short time, a sphere of nearly 

 mathematical perfection ; but the contact of a foreign body 

 destroys at once the uniformity of tension on which its exist- 

 ence depends, producing undue strain at one particular part, 

 and so the unmanageable beauty commits suicide at a touch. 

 If our plaything escape the profaning touch of anything less 

 fairy-like than itself (and I may here remark that they have a 

 great dislike to touching one another, being brought into actual 

 contact with difficulty), it contains within its own constitution 

 elements of destruction. For the film of which it is made, 

 thin though it be, is liquid, and must, therefore, obey the 

 liquid laws ; hence the solution gradually runs down to the 

 lowest point, till the upper surface becomes so thin that it can 

 no longer support the strain to which it is exposed, and the 



