614 PLATEAU ON THE PHiENOMENA OF A FREE LIQUID MASS 



plate of the same diameter perforated by a large aperture (fig. 8). 

 This plate having been turned in a lathe, I was certain of its being 

 perfectly circular, which would be a very difficult condition to 

 fulfill in the case of a simple curved iron wire. In the second 

 place, I took for the solid part of the doubly concave lens, a band 

 of about 2 centimetres in breadth, and curved into a cylinder 

 3i centimetres in diameter. These two systems were arranged 

 as in fig. 9, in such a manner that the entire apparatus being 

 suspended vertically in the alcoholic mixture by the iron-wire a, 

 and the two liquid lenses being formed, their two centres were at 

 the same height, and 10 centimetres distant from each other. In 

 this arrangement the telescope cannot be adjusted by altering 

 the distance between the objective and the eye-piece ; but this 

 end is attained by varying the curvatures of these two lenses. 

 With the aid of a few preliminary experiments, I easily managed 

 to obtain an excellent Galilean telescope, magnifying distant ob- 

 jects about twice, like a common opera-glass, and giving per- 

 fectly distinct images with very little irisation. Fig. 10, which 

 represents a section of the system, shows the two lenses com- 

 bined. 



Figures of equilibrium terminated by plane surfaces. Liquid 

 polyhedra. Laminar figures of equilibrium. 



30. In the experiment detailed at paragi'aph 21, we obtained 

 a figui'c presenting plane surfaces. These were two in number, 

 parallel, and bounded by circular peripheries ; but it is evident 

 that these conditions are not necessary in oi'der to allow plane sur- 

 faces to belong to a liquid mass in equilibrium. We can under- 

 stand that the forms of the solid contours might be indifferent pro- 

 vided they constitute plane figures. We can moreover under- 

 stand, that the number and the relative directions of the plane 

 surfaces may be a matter of indifference, because these circum- 

 stances exert no influence upon the pressures which correspond 

 to these surfaces, pressures which will always remain equal to 

 each other. Lastly, it foUovys from the principle at which we 

 arrived at the end of paragraph 20, relative to the influence of solid 

 wires, that for the establishment of the transition between a plane 

 and any other surface, a metallic thread representing the edge of 

 the angle of intersection of these two surfaces will be sufficient. 

 We are thus led to the curious result, that we ought to be able to 

 form polyhedra which are entirely liquid excepting at their edges. 



