600 PLATEAU ON THE PHENOMENA OF A FREE LIQUID MASS 



be less sensible in proportion to the thinness of the wire in 

 question. Fig. 3 represents the result of the experiment with 

 two unequal segments. The discontinuity of the curvatures is 

 a very general fact, which we shall frequently find to recur in 

 the course of our experiments ; it will hereafter lead us to very 

 important consequences. 



15. I have repeated the same experiment, substituting a plate 

 of an elliptic form for the circular plate. In this, as in the 

 preceding case, the oil extends over both faces of the solid, so as 

 entirely to cover them ; and, if the volume of the liquid mass is 

 not too great, the curvatures again terminate abruptly along 

 the rim of the plate. By gradually augmenting the volume of 

 the primitive sphere of oil, without however rendering it suffi- 

 ciently large to allow of the mass completely enveloping the 

 plate so as to retain the spherical form, a limit is attained at 

 which the edge of the plate ceases to reach the superficial layer 

 of the new figure of equilibrium except at the two summits of 

 the ellipse. The discontinuity in the curvatures then only occurs 

 at these two places. Figs. 4 and 5 exhibit the result of the ex- 

 periment in this case. In fig. 4 the long axis of the ellipse is 

 presented to view, in fig. 5 its short axis. 



16. All the facts which we have hitherto detailed show, 

 that so long as the interior of the mass is modified, its ex- 

 ternal shape undergoes no alteration ; but that directly the super- 

 ficial layer is acted upon, the mass acquires a different form. To 

 complete the proof, by experiment alone, that the configuring 

 actions exerted by the liquid upon itself emanate solely from the 

 superficial layer, the only point would then be the possibility of 

 reducing a liquid mass to its superficial layer, or at least to a 

 thin pellicle, and to see if in this state it would assume the same 

 figure of equilibrium as a complete mass. Now this is completely 

 realized in soap-bubbles ; for these bubbles, when detached from 

 the tube in which they have been made, assume, as is well 

 known, a spherical form, i. e. the same figure as that which we 

 find a complete mass acquires in our apparatus, when with- 

 drawn from the action of gravity and perfectly free. When 

 the mass adheres to a solid system, which modifies its figure, 

 it is clear that the entire configurative action is composed of 

 two parts, one of which belongs to the solid system ; and we 

 find that this system only exerts it when acting upon the su- 

 perficial layer; the other belongs to the liquid, and emanates 



