634 PLATEAU ON THE PHENOMENA OF A FREE LIQUID MASS 



give greater stability to the mass, and thus to prevent the move- 

 ments in question from producing the disunion. 



46. It might be asked, whether the want of symmetry, which 

 is constantly seen in the spontaneous modification of the above 

 unstable figures, is the result of a law which governs these 

 figures ; or whether it simply arises, as we should be led to be- 

 lieve at first sight, from imperceptible differences still existing 

 between the densities of the two liquids, which differences acting 

 upon unstable figures might produce this want of symmetry, 

 notwithstanding their extreme minuteness. 



After having concluded the preceding experiments, I imagined 

 that to solve the question in point, all that would be requisite 

 would be to ari'ange matters so that the axis of the figure, in- 

 stead of being vertical, as in the above experiments, should have 

 a horizontal direction. In fact, in the latter case, the slightest 

 difference between the densities ought to have the effect of 

 slightly curving the figure, but evidently cannot give the liquid 

 any tendency to move in greater quantity towards one exti'emity 

 of the figure than the other ; whence it follows, that, if the spon- 

 taneous alteration of the figux'e still occurs unsymmetrically, this 

 can only be owing to a peculiar law. 



On the other hand, if the figure really tends of itself to change 

 its form unsymmetrically, it is clear, that, in the case of the ver- 

 tical position of the axis, the effect of a trace of difference be- 

 tween the densities ought to concur with that of the instability, 

 and thus to accelerate the moment at which the figure com- 

 mences to alter spontaneously. Consequently, on avoiding this 

 extraneous cause by the horizontal direction of the axis of the 

 figure, we may hope to approximate more nearly to the cylin- 

 drical form, or even to attain it exactly; we can moreover un- 

 derstand, that the difficulty in the operations will be found 

 to be considerably diminished. 



I therefore constructed a solid system, presenting two vertical 

 discs of the same diameter, placed parallel with each other, at 

 the same height, and opposite each other. Each of these discs 

 is supported by an iron wire fixed normally to its centre, then 

 bent vertically downwards, and the lower extremities of these 

 two wires are attached to a horizontal axis furnished with four 

 small feet. This system is represented in perspective in fig. 27. 

 The diameter of the discs is 30 millims., but the distance which 

 separates them is not four times this diameter. I thought that 



