358 Prof. J. Plateau on the Figures of Equilibrium 



According to figures represented on an Etruscan vase preserved 

 in the Museum of the Louvre, it appears that even in ancient 

 times children amused themselves with blowing complete bubbles. 

 With regard to modern times, I will content myself in this ex- 

 tract with saying that the colours, tension, pressure, average 

 thickness, persistence, constitution, and different modes of pro- 

 duction of the films, the phenomena of endosmose exhibited by 

 them, a few special facts and applications, the form of certain 

 films, and, subsequently to my investigations, of systems of films 

 have been made the subject of these observations. 



Before returning to the general questions connected with the 

 figures of equilibrium, I discuss in the present Series two phe- 

 nomena, the discussion of which could not well be brought in 

 elsewhere. 



As every one knows, the ascent of liquids in tubes, the sides 

 of which they are able to wet, does not take place to any consi- 

 derable extent except when the internal diameters of the tubes 

 are very small, whence has arisen the expression capillary pheno- 

 mena ; and gravity always puts a limit to the height of the column 

 that is raised. But if the action of gravity were neutralized, 

 these limitations ought to disappear, and a liquid ought to be 

 able to rise to any height in a tube of any diameter. 



It appeared to me to be interesting to try this application of 

 my processes, by using either oil surrounded by the alcoholic 

 liquid, or the alcoholic liquid surrounded by oil. The tubes that 

 I employed were both of them 42 centims. long, and one 14 and 

 the other 15 centims. in internal diameter. I describe in the me- 

 moir a series of indispensable precautions, which it would occupy 

 too much space to mention here, and by means of which the ex- 

 periments completely succeeded. The oil in one of the tubes and 

 the alcoholic mixture in the other rose gradually to the top ; the 

 motion of the oil, however, was retarded, while that of the alco- 

 holic mixture was accelerated. The oil required 21 minutes 

 1 second in order to rise 4 decims. ; the first decimetre was 

 traversed in 1 minute 47 seconds, and the fourth in 9 minutes. 

 To rise in like manner 4 decimetres, the alcoholic mixture took 

 only 5 minutes 55 seconds ; it accomplished the first decimetre 

 in 1 minute 42 seconds, and the fourth in 1 minute 16 seconds. 



The second fact that I discuss here is the constitution of a 

 current of gas traversing a liquid. A current of air issuing 

 from a round hole and rising through a liquid may be considered 

 as the converse of a liquid vein projected downwards through the 

 air from a similar round hole. I prove that, apart from mole- 

 cular figurative forces, the forms of the current of gas would be 

 completely analogous to that of the liquid vein, also considered 

 as not subject to figurative forces. In both cases the form would 



