212 TUB FIGURES OF EQUILIBRIUM OF A LIQUID MASS 



which occurred to me. The oil ainl the alcoliolic liquor were enclosed in dif- 

 ferent flasks, and the latter contained a very slight excess of alcohol. Uaving, 

 by chance, carried these two flasks into a room warmer than that in which they 

 had been, I iirst introduced into the mixture a certain quantity of oil, which, by 

 reason of the slight excess of alcohol, descended slowly to the bottom of the 

 flask. A short time afterwards I poured in another quantity of oil, and I was 

 Burprised to sec this, on the contrary, rise towards the upper part of ihc mix- 

 ture. The reason of the singular difference was this : the alcoholic mixture 

 inclosed in one of the flasks was very considerable in quantity relatively to the 

 oil which the otlier contained. Now, at the first moment the liquids, not 

 having sensibly changed their temperature, maintained betAveen them the same 

 relation of density ; but after a short time the oil, by reason of its small volume, 

 having become warmer than the alcoholic mixture, had thus become relatively 

 lighter. The warmth of the hand which held the flask in pouring out the oil 

 must have also contributed to the effect in question. 



8. Now let us suppose a fine sphere of oil in permanent equilibrium in the 

 surrounding liquid, and let us endeavor to submit it to other forces than its 

 own attracti(m.s. 



The first idea which presents itself is to try the action of centrifugal force. 

 For this purpose it is necessary to impress on the sphere of oil a mnvement of 

 rotation around one of its diameters, and which is effected by introducing into 

 this sphere a small metallic disc, which is made to turn upon itself by means 

 of an axis which traverses it perpendicularly. This disc carries the oil with it 

 by its adherence, and the whole mass of this liquid takes a movement of rotation. 



Before explaining the effects which result from this movement, I shall describe 

 in detail the apparatus I have employed — an apparatus by the aid of which all 

 the experiments succeeded perfectly and with the greatest facility. It is rep- 

 resented in fig. 1. 



Fig. 1. 



The vessel is with plane sides, formed of rectangular plates of glass set in 

 an iron frame ; the sides are each 25 centimetres br^ad and 20 high. The 

 small disc and its axis are also of iron, a metal whose prolonged contact with 

 oil does not stain it as copper does. The diameter of the disc is about 35 milli- 

 metres, and the axis is formed of an iron AVire about H millimetre thick. 'Jliis 



