WITHDRAWN FROM THE ACTION OF GRAVITY. 239 



ceeding, a layer of oil witli plane faces. This is, in fact, confirmed by expe- 

 rience, as we shall see further on. 



19. To render the curvatures of the liquid lens very slight, the point of the 

 ' syringe must naturally be applied to the middle of the lens, because the maxi- 

 mum of thickness exists there. Now, when a certain limit has been attained, 

 the mass suddenly becomes divided at that point, and a curious phenomenon is 

 produced. The licjuid rapidly retires in every direction towards the metallic 

 circumference, and forms a beautiful liquid ring along the latter; but this ring 

 does not last for more than one or two seconds, after which it spontaneously 

 resolves itself into several small, almost spherical masses, adhering to various parts 

 of the ring of iron wn-e, which passes through them like the beads of a necklace. 



20. The reasoning which led us, at the commencement of paragraph 18, to 

 reduce the primitive solid system to a simple metallic wire representing- the line 

 in the direction of which this system is met'by the superficial layer belonging 

 to the new figure of equilibrium, may be generalized. We may conclude that 

 whenever a solid s^'stem introduced into the mass is not met by the superficial 

 layer of the figure produced, excepting in the direction of small lines only, sim- 

 ple iron wires, representing the lines in question, may be substituted for the 

 solid system employed. But if the volume of the primitive solid system were 

 considerable, it would evidently be requisite to add to the mass of oil an equiva- 

 lent volume of this liquid, to occupy the place of the solid parts suppressed. 



There is, however, an exception to this principle ; it occurs when the solid 

 system separates the entire mass into isolated portions, as in the experiment of 

 paragraph 14 ; for then these portions assume figures independent of each other, 

 and Avhich may correspond to different pressures. In this case the suppression 

 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 gen- 

 eral, and the result of it is that well-developed eff"ccts of configuration may be 

 obtained on employing simple iron wires instead of solid systems. The experi- 

 ment 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 superficial 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, de- 

 termine a sudden transition between these two portions of the surface, the curv- 

 atures of which Avill 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 ex- 

 erted 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 experi- 

 ment is able to teach us in regard to plane surfaces and concave ^^^^ 

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

 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 phenomena 

 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 



