232 THE FIGURES OF EQUILIBRIUM OF A LIQUID MASS 



out of the question, its sole function being to neutralize the action of gravity 

 upon the masri forming the object of the experiments. 



9. We f^llall now pass to the experimental part. And first, to avoid useless 

 rt'iJetition, we shall say a few words relative to the apparatus to be used. As 

 tin; liquid always consists of a mass of oil immersed in an alcoholic mixture of 

 the same density as itself, our solid systems will all consist of iron, and this for 

 the following reasons : In ordinary circumstances oil contracts, I beHeve, per- 

 fect adhesion with all solids ; but this is not exactly the case when the same 

 oil is plunged into a mixture of water and alcohol ; for then, in the case of cer- 

 tahi solids, as, e.g., glass, the phenomena of adhesion sometimes undergo modi- 

 fications which give rise to trouble in the experiments. Wc shall meet with 

 an instance of this in the subsequent parts of this memoir. Now, the metals 

 do not ]nesent this inconvenience ; moreover, the form which we have given to 

 most of our solid systems would render their construction of any other sub- 

 stance besides a ruetal difficult. Now, among metals we prefer iron, not copper, 

 because oil removes nothing from iron, whilst by prolonged contact with copper 

 it slightly attacks it, acquires a green color, and increases in density, which is 

 a great inconvenience.* 



When we wish to use one of tlicse solid systems of iron, before introducing 

 it into the vessel, it must be completely moistened with oil; and for this pur- 

 pose it is not sufficient simply to immerse it in this liquid, but it must be care- 

 fully rubbed with the finger. The presence of this coating facilitates the 

 adherence of the liquid mass. 



We shall continue to make use of the vessel with plane walls, described in 

 the preccdiiig memoir, § 8;t a common-shaped bottle, and the flask previously 

 mentioned (§§ 5 and 8) in the same memoir, are not well adapted, because they 

 do. not exhibit the true figure of the mass. 



When the solid system is composed of a single piece, it is supported by a 

 vertical iron wire, which is screwed to the low^er end of the axis traversing the 

 metallic stopper ; but for certain experiments the solid system is formed of two 

 isolated parts, and then only one of them is attached to the axis, as I have 

 stated ; the other is supported by small feet which rest upon the bottom of the 

 vessel. It need not be mentioned that those liquids only which are prepared 

 in such a manner as to be incapable of exerting any chemical action upon each 

 other can be employed, (§§ 6 and 24 of the preceding memoir.) 



In addition to the little funnel for introducing the mass of oil into the vessel, 

 the iron wire which serves for uniting the isolated spheres, &c., of which I have 

 spoken in the preceding memoir, the experiments require some other accessory 

 instruments, as, in the first place, a small glass syringe, the point of which is 

 elongated and slightly bent. It is used as a sucking-pump, to remove, for in- 



* In a, letter wliicli Dr. Famday did me the honor of sending' to me, regarding the pre- 

 cetliug memoir, he informed me lluit, when about to repeat my experiments before a nuu;erous 

 audicuee, wishing to produce a still greater ditfercuce in the aspect of the tAvo liquids, he 

 dissolved intentionally a little oxide of copper in the oil, so as to render tlie latter of a green 

 color. The compound having thus been made beforehand, and rendered perfectly liomoge- 

 neous, and the ulcoliolic mixlure having been regulated according to the density of the modi- 

 tied oil, the presence of the copper in solution could not produce any inconvenience ; but in 

 this case also tlie solid systems should unquestionably be made of iron. ' 



tin making tlie experiments rela.ing to the present memoir, I found that it was requisite 

 slightly to mo<lify tlie apparatus in question. The second perlbration in the plate forming 

 the lid of the vessel should be but htlle smaller than the centrat aperture ; its neck should be 

 less elevated; and, lastly, it should be placed near the other; if left as previously described 

 and figured, tlie emi)loyment of the accessory instruments which we shall iTescribe would be 

 imi)0ssihle. Aloreover, the neck of the central aperture should be furnished with a slight 

 rim, so that it may be easily taken hold of when we wish to remove the lid, as, e.g., v. hen it 

 is required to attach a solid system which is too large to pass through this same aperture to 

 thoa.'cis which traverses the stopper. Lastly, the vessel should be fumishea with a stop 

 cock at its lower part, so that it may be easily emptied. 



