606 PLATEAU ON THE PH^NOMEXA OF A FREE LIQUID MASS 



pression of one portion of the solid system would place the 

 figures primitively isolated in communication, and the inequality 

 of the pressures would necessarily induce a change in the whole 

 figure. Excluding this exception, the principle is general, and the 

 result of it is that well-developed effects of configuration may be 

 obtained on employing simple iron wires instead of solid systems. 

 The experiment of the biconvex lens furnishes one instance of 

 this, and we shall meet with a great many others hereafter. 

 Nevertheless, to be enabled to comprehend the influence of a 

 simple metallic wire upon the configuration of the liquid mass, it 

 is not requisite to consider this wire as substituted for a complete 

 solid system ; it may also be considered by itself. It is, in fact, 

 clear that the solid wire acting by attraction upon the super- 

 ficial layer of the mass, the curvatures of the two portions of the 

 surface resting upon it ought not to have any further relation of 

 continuity with each other. The metallic wire may therefore 

 determine a sudden transition between these two portions of the 

 surface, the curvatures of which will terminate abruptly at the 

 limit which it places to them. The principles which we have 

 established ought undoubtedly to be considered as among the 

 most remarkable and curious consequences of the principle of 

 the superficial layer, and one cannot avoid being astonished 

 when we see the liquid maintained in such different forms by an 

 action exerted upon the extremely minute parts of the superficial 

 layer of the mass. 



21. We have experimentally studied the influence of convex 

 surfaces of spherical curvature ; let us now ascertain what expe- 

 riment is able to teach us in regard to plane surfaces and concave 

 surfaces of spherical curvature. Let us take for the solid system 

 a large strip of iron, curved circularly so as to form a hollow 

 cylinder, and attached to the suspending iron wire by some point 

 on its outer surface (fig. 7)' To prevent the production of 

 accessory phaenomena in the experiment, we shall suppose that 

 the breadth of the metallic band is less than the diameter of the 

 cylinder formed by the same band, or that it is at least equal to 

 it. Make the mass of oil adhere to the internal surface of this 

 system, and let us suppose that the liquid is in sufficient quan- 

 tity then to project outside the cylinder. In this case the mass 

 will present on each side a convex surface of spherical curvature, 

 and the curvatures of these two surfaces will be equal. This 

 figure is a consequence of what we have previously seen, and we 



