20l> 



Professor Sir James Dewar 



[Jan. 19, 



change of diameter are observed. The coloured area is seen to 

 change from steel-bhie to bhie-purpl ; through magenta and deep 

 amber until ahnost the whole of it is a full golden colour as a result 

 of the diminished thickness, which however is still of the order of 

 fifteen times that of the l)lack. During this time tlie black bountiary 

 has risen slightly in level ; but when the area of the black zone is 

 calculated at successive stages, the value is found to remain constant 

 to within a few per cent. All liquid must be well drained from 

 the hanging bubble by leaving a drainage tube in contact with 

 the drop position, during the preliminary development to partial 

 blackness. Two sets of observations, showing the approximate con- 

 stancy of the area of the black zone, while the coloured portion 

 is varying to a large ratio. p,ppear in Table 1 l)elow. 



Table 10. 



Wliole Bubble 



Black Zont 



Coloured Zone 



Tlius, from the liist four observations, the a 

 the first ))u]}ble only varied some '1 per cent, from its mean 



ctiij^l l)lack area 



of 

 value 



1)2*7 cm.^, while the coloured-to-l)lack ratio fell from 9*7 to 3 '6, or 

 some 63 per cent. : similarly the actual black aiea of the second 

 bubble varied about 5 per cent, from its mean value 74 ".^ cm.-, while 

 the coloured area fell from nearly 14 times to 3i timei the black 

 area — a drop of over 7.') per cent. 



Absorption ok Water by Bubbles Oomposed of Oleate 

 ( ; lycerixe Solution. 



When i)oiled water is introduced into a vessel which liolds a 

 bubble composed })artly of glycerine, water vapour is absorbed and 



