1917] on Soap Bubbles of Long Duration 185 



thickness to show colour, 22*7 cm. diameter, thinned to all black 

 (thinnest possible), 23 cm. diameter. 



A coloured bubble 43 "3 cm. diameter, thickened in 15 minutes by 

 condensation to 42-7 cm. diameter. 



Bubbles of such a size flattened down on their supporting rings 

 as they became thicker and heavier, and could be seen hanging over 

 the ring-support from this cause. 



A bubble 39 cm. diameter, hanging from a 4-cm. glass funnel 

 support, thinned to over 70 per cent, black on its second day, and 

 increased until its 63rd day, when it burst, 80 per. cent, bhick. On 

 five occasions a slowly accumulated drop was observed to fall off 

 — namely, on the 6th, 10th, 20th, 27th, and 52nd days respectively. 

 The alterations in diameter which thereupon resulted were as follow : — - 



This bubble was blown from a solution containing 10 per cent, 

 ammonium oleate and 50 per cent, of glycerine. 



A bubble of similar size, but resting on a ring, varied in vertical 

 diameter as follows : — 



42 • 6 cm. when fairly thick, at first. 

 43-5 „ 15th day. 

 43*0 „ 16th day, orange to amber. 

 43*3 „ 17th day, 80 per cent, black. 

 43*0 „ 18th day, four-fifths deep orange, one-fifth purple ; 

 thus rising higher on its ring-support as it became thinner. 



The maximum amount of distortion by loading which a bubble of 

 this size cm maintain was observed in one case by expanding the 

 bubble until the distortion at the rim-support, 4 cm. in diameter, 

 showed that it was nearly being dragged off. The dimensions were 

 then 45 • 4 cm. vertically and 40 - 1 cm. horizontally (ellipticity 11*7 per 

 cent,). The diminution in vertical diameter by the release of a single 

 drop was 2'1 cm., showing the near approach to instability. After 

 fourteen days the drainage reduced the loading of the bubble so that 

 the vertical diameter became substantially constant, as shown by the 

 following records : — 



Day . . 7th. 14th. 21st. 



Diameter . 44*3 41-6 41-8 



After this date the bubble remained coloured in the lower three- 

 fourths of its area. In this condition the distortion caused by one 

 drop was approximately 1 cm. The persistence of the coloured stage 

 could be maintained by a very minute continuous leak of soliltion 

 from the reservoir into the supporting nozzle. When the soap 



