622 PLATEAU ON THE PHifiNOMENA OP A FREE LIQUID MASS 



two rings is represented in Plate VII. fig. 20 bis ; the diameter 

 of those which I employed was 7 centims. 



After having raised the upper ring as much as possible, let 

 a sphere of oil, of a slightly larger diameter than that of the 

 rings, be formed, and conducted towards the lower ring, in 

 such a manner as to make it adhere to the entire circum- 

 ference of the latter; then depress the upper ring until it 

 comes into contact with the liquid mass and the latter is uni- 

 formly attached to it. When the mass has thus become ad- 

 herent to the system of the two rings, let the upper ring be 

 slowly raised ; when the two rings are at a proper distance apart, 

 the liquid will then assume the form the vertical projection of 

 which is represented in fig. 21, in which the lines a b and c d are 

 the projections of the rings. The two portions of the surface 

 which are respectively applied to each of the rings are convex 

 spherical segments ; and the portion included between the two 

 rings constitutes a figure of revolution, the meridional curve of 

 which, as is shown, is convex externally. We sliall recur, in the 

 following series, to this part of the liquid figure. If we now 

 continue gradually to raise the upper ring, the curvature of the 

 two extremities and the meridional curvature of the intermediate 

 portion will be diminished ; and if there is exact equilibrium 

 between the density of the oil and the surrounding liquid, the 

 surface included between the two rings will be seen to assume a 

 perfectly cylindrical form (fig. 22). The two bases of the liquid 

 figure are still convex spherical segments, but their curvature is 

 less than in the preceding figure. If the interval between the 

 rings be still further increased, it is evident that the surface in- 

 cluded between them would lose the cylindrical form, and that 

 a new figure would result. This is what occurs ; but the consi- 

 deration of the figure thus produced must be deferred. 



Instead then of immediately increasing the distance between 

 the rings, let us commence by adding a certain quantity of oil 

 to the mass, which will again render the surface included be- 

 tween the rings convex. Let us then gradually elevate the 

 upper ring, and we shall produce a cylinder of greater height 

 than the first. If we repeat the same manipulation a suitable 

 number of times, we shalf ultimately obtain the cylinder of the 

 greatest height which our apparatus permits. I have in this 

 manner obtained a perfectly cylindrical mass 7 centims. in dia- 

 meter and about 14 centims. in height (fig. 23). To allow of 



