1917] 



on Soap Bubbles of Long Duration 



181 



Fig 1. The liquid air is contained in a tube A, which is litted by a 

 ground cap to the delivery tube B, and placed in a vacuum vessel D 

 to control heat influx. At B one branch tube leads to the thistle- 

 shaped funnel from which the bubble is to be suspended, while 

 another branch leads to the stop-cock C, by means of which the 

 admission of air into the bubble can be regulated. The cavity above 

 the ground cap, and the horizontal tube leading to the bubble are 

 packed with copper-wire gauze in order to warm the air evaporated. 



----R 



Fig. 1. 



The soap solution is supplied to the mouth of the thistle-shaped 

 funnel in the usual way : or otherwise, by having a constriction in 

 the tube above the thistle-shaped funnel, together with a stoppered 

 dropping funnel. It is thus possible to fill the constriction with soap 

 solution, and develop bubbles singly or in succession, as desired. 



Apparatus for the Productiox of Bubbles under 

 Various Pressures. 



The apparatus. Fig. 2, is a spherical glass flask A of 2 J litres 

 capacity, fitted with an india-rubljer cork which has been previously 

 cut and steamed in order to remove volatile organic matter. The 



