WITHDRAWN FROM THE ACTION OF GRAVITY. 615 



Now this is completely verified by experiment. If for the solid 

 system we take a frame-work of iron wire representing all the 

 edges of any polyhedron, and we cause a mass of oil of the proper 

 vohime to adhere to this frame-work, we obtain, in fact, in a per- 

 fect manner, the polyhedron in question ; and the curious spec- 

 tacle is thus obtained of parallelopipedons, prisms, &c., com- 

 posed of oil, and the only solid part of which is their edges. 



To produce the adhesion of the liquid mass to the entire 

 frame-work, a volume is first given to the mass slightly larger 

 than that of the polyhedron which it is to form ; it is then placed 

 in the frame- work ; and lastly, by means of the iron spatula 

 (§ 9), which must be introduced by the second aperture of the 

 lid of the vessel, and which is made to penetrate the mass, the 

 latter is readily made to attach itself successive!}' to the entire 

 length of each of the solid edges. The excess of oil is then gra- 

 dually removed with the syringe, and all the surfaces thus be- 

 come simultaneously exactly plane. But that this end may be 

 attained in a complete manner, it is clearly requisite that the 

 equilibrium of density between the oil and the alcoholic mixture 

 should be perfectly established ; and the slightest difference in 

 this respect is sufficient to alter the surfaces sensibly. It should 

 also be borne in mind, that the manipulation with the spatula 

 sometimes occasions the introduction of alcoholic bubbles into 

 the interior of the mass of oil ; these are, however, easily re- 

 moved by means of the syringe. 



31. Now, having formed a polyhedron, let us see what will 

 happen if we gradually remove some of the liquid. Let us take, 

 for instance, the cube, the solid frame- work of which, with its 

 suspending wire, is represented at fig. 11*. Let the point of 

 the syringe be ajjplied near the middle of one of the faces, and 

 let a small quantity of the oil be drawn up. All the faces will 

 immediately become depressed simultaneously and to the same 

 extent, so that the superficial square contours will form the bases 

 of six similar hollow figures. We should have imagined this to 

 have been the case for the maintenance of equality between the 

 ])ressure8. 



If fresh portions of the liquid are removed, the faces will 



become more and more hollowed ; but to understand what 



happens when this manipulation is continued, we must here 



enunciate a preliminary proposition. Suppose that a square 



• The edges of all the frames which I used were 7 centiins. in length. 



