£gg WAYES BETWEEN OIL AND WATER. 



the first has more of the heavier liquid and less of the lighter, 

 the second more of the lighter and less of the heavier. 

 Conditions ne- For these two columns to acquire their level it is necessary, 

 cessary to its that the first should lose a portion of the heavier liquid and 

 icstorauon. aC q U j re a portion of the lighter, and the second the contrary. 

 And as there is no cause to produce this effect but the por- 

 tion of the heavier liquid that one column has more than 

 the other, the reduction of the inferior liquid to a level can- 

 not be effected by the absolute gravity of the liquid as hap« 

 pens when it is alone in a vessel, but must be caused only 

 by the excess of the weight of the inferior liquid over that 

 of the superior. 

 The equili- Hence it follows in the first place, that, as the restoration 



tmum more of the level of the inferior liquid is the effect of a very small 

 stoTed ^ part of its gravity only, it must be extremely slow, and in 

 consequence capable of being observed more easily, than 

 when this liquid is alone in the vessel. It may not be amiss 

 to observe however, that this cause, however small it may 

 be, being a gravitating action, must retain its nature of an 

 accelerating force, and thus produce an undulatory motion 

 as in ordinary circumstances. 

 and its disturb- ^ now we atten{ * to l ^ e interruption of equilibrium, or of 

 ance more the level, between the several columns of the inferior liquid, 

 conspicuous, we g-^gn fi n( \ t t h a t. the same cause, which renders the restora- 

 tion of the equilibrium slower and more obvious, renders its 

 interruption likewise more considerable. 

 This scarcely Gravitation, as it exists before our eyes, imparts to ordi- 

 obsenred with nary bodies, in the shortest space of time we can estimate, a 

 ^sing e liquid. ve i oc jty very similar to those which we ourselves very com- 

 monly produce: so that when we do any thing to disturb 

 the level of a liquid surface it is restored almost immediately* 

 If we give a moderate inclination to a vessel filled with a 

 liquid, the level is restored in proportion as we endeavour 

 to destroy it; so that it requires some little knowledge of 

 natural physiology to be aware, that it lias been disturbed 

 and restored. 

 Caseoftwo But in the circumstances in which the inferior liquor is 



'iquids placed ; as but a small portion of its gravity remains to reduce 



it to a level, it is evident, that it cannot effect this with the 

 same promptitude; and that, if the same motion be em- 

 ployed 



