!?08 THE FIGURES OF EQUILIBRIUM OF A LIQUID MASS 



But llic difference of the two forces is still more strikingly exhibited by the 

 differcnci; of ilieir t^plieres of attraction. Irt the case of gravitation every atom, 

 for eXiinipUs of the earth attracts every other atom of the whole mass, eacff* 

 conspiring with all the others to produce the; spherical form. While under the 

 influence of molecular attraction the atoms of a li([uid globule only acts upon 

 the other atoms which are immediately around them; and hence the atoms in 

 the interior of a globule are, as it were, in a neutral condition, attracted e(|U.illy 

 in everv direction. The only atoms, therefore, which arc active in j)roduciiig 

 the globular forms and in giving rise to the phenomena described in this 

 memoir, are those at the suifice of the liquid, since these are only attracted on 

 one side, and are, therefore, free to exert their eneig}' towards the mass, and 

 their tendency to bring this into the smallest compass, namely, that of a sphere. 

 According to this view a globuh; of water may be considered an assemblage of 

 atoms, without attraction, compressed into the; spherical form by a contractile 

 film, within which the atoms are enclosed. The amount of contractile force 

 of such a lilm will depend on the energy of the attraction between the con- 

 tiguous atoms and the degrees of cnrvarurc. To illustrate tliis, let us suj)pose 

 a slip of lndia-rubb(;r to b(; stretched horizontally between two supports. If to 

 the middle of this we attach a small weight, the slip will sag downwards, and 

 the point to which the weight is attached will descend until there is an equi- 

 librium between the weight and the contractile force. If an additional weight 

 be attached, tli(^ descent will be increased until a new equilibrium is attained, 

 and so on, the contractile i'orce will increase with the d(>gree of bending. A 

 pimilar force is exerteil at the free surface of all li(iuids. If this surface is hori- 

 zontal, the attraction will be equal in ever}' direction in the horizontal plane; 

 but if at any point w(! press the surface so as to bei;d it out of this j)lane, the 

 contractile ibrce will be called forth, tending to bring the ])oint back into its 

 former position. It is this surfaces contractile force which causes a small globule 

 of water or mercury, when ilattened, to spring back into the spherical form 

 when the compressing force is removed. The more the globule is compressed, 

 or the greater the curvature at the circumference, the greater will be the resist- 

 ance. Hence, also, the smaller the bubble the greater will be the contractile 

 power of its surfaces, and the more energetically will it assume the spherical 

 form. This is converse of the action of gravity, the tendency of which to 

 produce the globular form will be the greater in proportion to the greater size, 

 and consequently less curvature of the surface. 



These remarks will enable the reader to comprehend more definitely the 

 nature of the phenomena exhibited in the following paper. 



J. ll.l 



FIRST SERIES. 



1. Liquids, being gifted with an extreme molecular mobility, yield with 

 facility to the action offerees which tend to modify their exterior form. Bat 

 amongst these forces there is one which predominates so much over the. rest 

 that it almost entirely masks their action. This ibrce is gravity; this it is 

 which cjaises licjuids to asj-ume the form of vessels which contain tliem ; and it 

 is this, also, which makes smooth and horizontal the portion of their surface 

 which remains free. We can scarcely recognize, along the c(uitour of this free 

 suriaee, a slight curve which reveals the action of the combimd forces of the 

 attraction of the liquid for itself, and of its adherence for the solid matter of the 

 vessel. Jt is only by observing very small lifjuid masses, upon which the rela- 

 tive action of gravity is thus weakened, tiial we can see the iniluence of otli(;r 

 forces upon the iigiire of these masses manifested in a very forcible manner. 

 Thus the small drops of liquid, placed u\Hm surfaces which they caiuiot moisten, 



