234 THE FIGURES OF EQUILIBRIUM OF A LIQUID MASS 



11. Again, lot us caui?e some kiud of solid system to penetrate the liquid 

 mass; but now let the mass be of too small a volume to be capable of com- 

 pletely enveloping this system. The latter will then necessarily reach the 

 eupcrlicial layer; and, if the princii)le in question be true, the figure of the 

 liquid mass will be modified, or, in other words, will cease to remain spherical. 

 This doi's really occur, as we might have expected ; the liquid mass becomes 

 extended at those portions of the solid system which project externally from 

 its surface ; it finally cither occupies the whole of these portions, or only a part 

 of their extent, according to the form and the dimensions of the solid system, 

 and thus assumes a new iigure of equilibrium. We shall meet with examples 

 of this hereafter, (§§14, l.O, 17.) 



12. Instead of causing the solid system to penetrate the interior of the liquid 

 mass, let it simply be placed in contact w^ith the external surface of the latter. 

 Au action being then established at a point of the superficial layer, equilibrium 

 must be destroyed, and the figure of the liquid mass ought again to be modified. 

 This really occui*s ; the mass becomes extended upon the surface presented to 

 it, and consequently acquires a different shape. This resttlt might also have 

 been anticipated from what occurs under ordinary circumstances, when a drop 

 of water is placed upon a previously moistened solid surface. ' One might be 

 induced to believe that, as regards the actual result, this case is referable to 

 that of tlic preceding paragraph or that in paragraph 10 ; for it appears that 

 the liquid mass, becoming extended upon the solid system so as to obtain the 

 new figure of equilibrium, should ultimately occupy or envelop this system in 

 the same manner as if the latter had been made to penetrate its interior directly. 

 Under certain circumstances this must occur ; but the experiments Avhich are 

 about to be related will show that under other circumstances the result is 

 totally different. 



13. Let us take for the solid system a thin circular plate,* attached by its 

 centre to the iron wire which supports it, (Fig. 1,) and let us pro'duce the 



J^;^ /. 



fi^. 2. 



adhesion of its lower surface to the upper part of the mass of oil.t Directly 

 contact is completely established, the oil extends rapidly over the surface pre- 



* TIic dianu'tcr of that which I have u.sed is 4 centimetres. I mention this diameter for 

 the sake of being' definite. It is evident tliat in onr experiments the diineusious of the appa- 

 ratus arc coiiip;etely arbitrary, except that if these dimensions exceed certain limits, the 

 operations will become euibanassing in cousequence of the large quantities of liquid which 

 would be icquiied. 



t In order that this operation may be effected with facility, the sphere of oil must first 

 remain in the surrounding liquid beneath the central aperture in the lid ; the plate being then 

 introduced into ilic vessel, we have merely to lower it by means of the axis traversing the 

 8toi)])cr to In-ing it towards tlie liquid mass. If the latter does not occupy the position in 

 question, it must be pieviously placed there l\y means of a spatula covered with linen, {^ 9.) 

 It must be remarked here, that true contact between the plate and the sphere of oil does not 

 ustuiliy ensue iumiediatcly ; a certain resistance has to be overcome, analogous to that treated 

 of in the note to paragraph 4 of the preceding memoir; but to overcome this, the liquid 

 sphere need only be gently moved by means of the jjlate. The slight resulting pressiure 

 Boon causes the rupture of the obstacle and the production of adhesion. 



