184 Professor Sir James Dewar [Jan. 19, 



admission of fiexil)]e glass supporting rings, or draining points, 

 where necessary. Thus, by means of the dropper. Fig. 3«, a fine 

 glass thread or wire can be passed down through the bul)ble, so 

 that the drop is removed and the distortion observed. Similarly, 

 through one of the openings in the lid of the cubical glass chamber, 

 a thin glass rod with an up-turned end, approaching the bubble 

 from below, can be employed to drain off any excess of liquid, and 

 thereafter to determine the changes effected in the vertical and 

 horizontal diameters. 



Distortion of Bubbles, Hanging or Supported. 



The following instances show the amount of distortion or ellip- 

 ticity, present in hanging bubbles, under different conditions : — 



A bubble, 19*1 cm. vertical diameter, 17*8 cm. horizontal 

 diameter (ellipticity 7 per cent.), when freshly blown from solution 

 of 5 per cent, potassium oleate, 50 per cent, glycerine, was only 

 feebly coloured, and therefore fairly thick. On the fourth day its 

 vertical diameter was 18*1 cm., and on fifth day 17 "7 cm., being 

 then sufficiently thinned to be well coloured. 



A bubble of 5 per cent, ammonium oleate in 50 per cent, 

 glycerine, measuring 17*25 cm. vertically and 16 '2 cm. horizontally 

 (ellipticity G per cent.), was at first only feebly coloured in the lower 

 one-fourth. By the third day the vertical diameter was reduced to 

 16*6 cm. from the reduction of mass, shown by an intensification of 

 the colouring. A bubble of this composition exposed to water vapour, 

 by running water into the containing vessel, will condense and absorb 

 the water vapour and become thickened again for a time. Such a 

 bubble of 30 cm. vertical diameter was dragged down by the water it 

 absorbed in one day to 31*8 cm., an elongation of 6 per cent. 



A bubble, 11-2 cm. diameter, with the upper half black and 

 lower half coloured, was reduced to 10 cm. diameter, when entirely 

 black, by drainage — i.e. a distortion of 12 per cent, vertically was 

 caused by the lower half of a thin black bubble thickening to show 

 colour by adding a few drops of soap solution. 



If instead of the bul)ble being supported from above it rests on a 

 suitable light ring support, it will ol)viously decrease in vertical 

 diameter when it becomes thickened and weighted. This was fre- 

 quently observed Avith l)ubblcs of about 40 cm. diameter, resting on 

 a 10 to 12- cm. ring of thin iron wire. 



With a water layer in the globe, considerable variations were noted 

 from day to day, e.g. — 



Thus, a bub})le coloured green and carmine, very brilliant but 

 fairly thick, 42 • cm. diameter, thinned to half black and half silvery 

 (next thicker colour to black), 43 • 6 cm. diameter. 



Another bubble coloured amber to pur])le, near lower limit of 



