WITHDRAWN FROM THE ACTION OF GRAVITY. 225 



dissolves some oil, and this in its turn probably dissolves some* alcoliol. It is 

 especially from the modilication which the oil undergoes that its great diminu- 

 tion of relative density results, (§ 6.) Xo\v, when the oil thus modified remains 

 exposed to the air, it passes again gradually to the state of fresh oil, and resumes 

 its former density. It is partly to avoid this that I have recommended the fun- 

 nels which enclose the filters to be kept constantly covered, and the oil to be 

 kept in a flask perfectly corked. As for the alcoholic mixture, it is evident that 

 this last precaution is ecjually necessary. 



25. Before I conclude, I must forewarn those persons who may wish to repeat 

 my experiments of two effects which sometimes occur, and which cause disturb- 

 ance in the operations if the experimenter does not know the means of pre- 

 venting or destroying them. 



When some oil is introduced into a mixture containing an excess of alcohol, it 

 happens sometimes that the mass which has sunk to the bottom of the vessel 

 contracts adherence with this bottom and spreads itself out more or less on its 

 surface. There is then no means of removing it entire ; but the spreading of 

 the adhesion may Joe prevented by contriving that the bottom of the vessel 

 should be occupied by a layer of a mixture more dense than the oil, (§ 9.) 



The second effect to which I allude is presented in the inverse case — that is 

 to say, when the sphere of oil, instead of reaching the bottom of the vessel, rises, 

 on the contrary, to the surface of the alcoholic Jiquor, either because this liquor 

 contains too little alcohol, or on account of a lowering of temperature, or because 

 we have not been able to \ise prepared oil. TVhen this happens the mass flat- 

 tens at first, more or less, at the surface of the mixture, as if this last opposed 

 "a. resistance to it. Then, after some time, it makes its way through, and then pre- 

 sents a portion of plane surface, more or less extended, on the level with that of the 

 alcoholic liquor. But what occasions trouble is, that then, so to speak, it has 

 contracted an adherence with this same surface, from which it is not detached 

 without great difficulty. It is, at first, easy to prevent the production of this 

 effect by pouring on the surface of the liquor a small layer of pure alcohol ; and 

 this same means will serve also to destroy the effect in question, if it is already 

 produced. In this latter case we may again invert the vessel with caution. 

 The movement thus imparted to the ambient liquor suffices, ordinarily, to detach 

 the mass of oil, with the exception of a small portion, which almost always re- 

 mains adhering to the surface. 



26. Lastly, I have already mentioned the fact that, after a certain number of 

 experiments, the oil becomes filled with small spherules of alcoholic liquor. 

 Now, reciprocally, the ambient alcoholic liquor is also often sprinkled with a 

 multitude of small spherules of oil. It is scarcely necessary to remark that, 

 when all these spherules have become too numerous, and we desire to restore 

 the liquids to their original transparency, this is easily accomplished by fillra- 

 tions similar to those of Avhich I have spoken above, (§ 24.) 



27. We have been hitherto engaged with the figures assumed by a liquid 

 mass abstracted from the action of gravity and submitted to the attraction of 

 its molecules, either when this mass is at rest, or when a movement of rotation 

 upon itself is imparted to it. Notwithstanding the difference of the laws which 

 the attractive forces follow in this case and in that of the large planetary masses, 

 we have seen produced, on a small scale, a striking representation of the 

 majority of the phenomena of configuration relative to the celestial bodies. In 

 the second part of this investigation we shall submit our liquid masses to new 

 forces, and Ave shall then see developed a series of phenomena quite as curious 

 but of a different class. 



Note. — Professor Faraday, who has repeated many of M. Plateau's remarkable and beau- 

 tiful experiments, coloured his oil green, for the purpose of rendering it more distinctly visible 

 in' the spirit, by dissolving in it a little oxide of copper. This, he states, is easily done by 

 heating a little oil with the oxide, and then mingling that with the rest. 

 15 S 



