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LIII. On some curious Effects of the Molecular Forces oj 

 Liquids. By G. Vander Mensbrugghe*. 



1. Formation of liquid bubbles in a peculiar condition. 



IN meteorology the question as to the state of the vapour in 

 mists is far from beiug definitively solved.; the hypothesis of 

 vesicles, although strongly opposed, is not yet disproved. It is 

 well known that one of the principal arguments against this hypo- 

 thesis is, that the mode of formation of these vesicles is inconceiv- 

 able. We are now acquainted, however, with an interesting fact 

 which shows that a liquid film, unclosed and of any curvature, may 

 take the form of a hollow sphere. This experiment has, in fact, 

 been described by M. Felix Plateau f, son of the illustrious phy- 

 sicist. The author operated, however, on soap-water solely; so 

 that it might be urged that his results do not, strictly considered, 

 apply to pure water. Thanks to special circumstances, however, 

 I have been able to prove that pure water comports itself in this 

 respect almost like soap-water. I observed it in the following 

 manner. 



Having thrown from a window, 12 metres above the ground, 

 some pure water contained in a cup, I noticed that the sheet of 

 liquid became transformed into hollow spheres whose greatest 

 diameters were about 4 centimetres in length; after a fall of 

 from 8 to 10 metres the bubbles burst, and became scattered 

 into innumerable droplets. 



I reproduced the phenomenon a great many times, with dis- 

 tilled water, by taking vessels of different forms and changing 

 the mode of projection ; I succeeded almost invariably, though 

 the bubbles varied greatly in number and diameter ; the greatest 

 diameter, however, did not exceed 5 or 6 centimetres. The 

 resolution of the liquid sheet into hollow spheres was effected 

 with greater rapidity the narrower the sheet and the greater its 

 curvature. This peculiarity, it may be observed, is easily ex- 

 plained; for the molecular pressure, directed towards the con- 

 cave part of the sheet, must necessarily increase with the curva- 

 ture of the liquid surface. 



The best results may be obtained thus : — A cup, about 10 cen- 

 timetres broad and three-quarters full, being taken, the water is 

 projected, with moderate velocity, by moving the hand from 

 left to right (for example), in order that the bubbles which are 

 formed may not mutually prevent themselves from being seen. 

 The operator must place himself at least 6 metres above the 



* From the Bulletins de V Acad. Roy. de Belgique, ser. 2. vol. xviii. No. 8. 



t " Sur un mode particulier de production de bulles de savon," Bull, de 

 VAcad. de Belgique, ser. 2. vol. xiii. p. 286. [Phil. Mag. S. 4. vol. xxvi. 

 p. 407.] 



