WITHDRAWN FROM THE ACTION OF GRAVITY. 



113 



Axis is fixed by its lower end into a hole pierced in the middle of the plate of 

 glass which forms the bottom of the vessel. This hole is closed below by a 

 small plate of iron cemented to the ,2:lass. The upper end of the axis is screwed 

 to a larger wire, which forms the prolongation of it, and which, held yn\\i a 

 moderate degree of friction, \a frottevient donx,] in apiece of which I shall speak 

 hereafter, receives at its other extremity the handle by means of Avhich the disc 

 is turned. When the whole system is in place the disc ought to be half way 

 up the vessel. The square plate of glass which closes the vessel above is 

 pieced with two openings, each furnished with an iron neck, which is closed 

 with a stopper of the same metal. One of these openings is in the middle of 

 the plate, and its diameter is 55 millimetres. It is through the stopper which 

 closes it that the rod passes, a frottement dcmx, which receives on the ofle side 

 the axis of the disc, and on the other the handle. (See figure 2.) The other 



F\s. 2. 



opening is smaller, and is placed near one of the angles of the plate. It serves 

 for introducing into the vessel either the metallic wire, by the aid of which we 

 unite the partial masses of oil, or additional portions of alcohol, or of mixture at 

 another degree, (§ 9,) &c., when these operations are to be performed without 

 removing the disc from its place. Lastly, this same plate is cemented into an 

 iron frame, which is turned up all round, so as to fit upon a vessel as a lid upon 

 a box. The upper edges of the vessel have been ground with emery all to- 

 gether, after their being placed in the frame, so that the upper plate of glass fits 

 exactly upon them ; and by rubbing these edges and the metallic stoppers with 

 a little oil, the vessel, when the plate and stoppers have been placed, may be 

 considered as perfectly closed and keeping the mixture without evaporation of 

 alcohol. 



In my apparatus the plates of glass are fixed to the metallic framing by a 

 resinous cement, and this is slightly attacked by the alcoholic mixture. It 

 would perhaps be better to use some glazier's putty ; for the alcoholic mixture, 

 being prepared so as not to act any more upon the oO, (§§ 6 and 24,) this latter 

 cement would probably not suffer any alteration. However, the resinous mastic 

 resists to such a degree, that I have been able to leave the alcoholic liquor, 

 without inconvenience, in the vessel for whole months. 



The apparatus which I have just described is the best suited for obtaining, 

 in all their beauty, the phenomena, which are the objects of these experiments; 

 b\it, as I have said above, a hollow sphere of glass of pretty large dimensions 

 might be used with less cost, and without too much disadvantage, at least for 

 the experiments treated of in this part of the memoir. This ought to be fur- 

 nished with two tubular openings, one of which would serve for introducing the 

 system of the disc, and the other would efi'ect the same object as the second 

 opening of which we have spoken above. 



I shall, however, in what follows, suppose all along that the plane-sided ves- 

 sel above described is the one employed. 



