WITHDRAWN FROM THE ACTION OF GRAVITY. 619 



nuity, that the summits of these pyramids should not constitute 

 simple points, but little concave surfaces. But as the curva- 

 tures of these minute surfaces are very great in every direction, 

 they would give rise to still far less pressure than those m hich 

 estabhsh the transitions between each pair of surfaces of the 

 layers; for in the latter there is no curvature in one direction. The 

 oil of the layers will therefore be driven with much greater force 

 towards the centre of the figure than towards the other parts of 

 the junctions of these layers. Again, the twelve layers termi- 

 nating in this same centre, the oil flows there simultaneously 

 from a large number of sources. These two concurrent causes 

 ought then, in conformity with experiment, to produce the rapid 

 reappearance of the small central mass ; and we can understand 

 why it is impossible to obtain the complete system of the pyra- 

 mids otherwise than during the action of the syringe. 



34. All the other polyhedric liquids become transformed, like 

 the cube, into laminar systems when the mass of which they are 

 composed is gradually diminished. Among these systems, some 

 are complete ; the others still contain very small masses, which 

 cannot be made to disappear entirely. Analogous considerations 

 to those which we applied with regard to the cube would show, 

 in each case, that the formation of layers commences as soon as 

 the hollow surfaces which would correspond to the ordinary law 

 of pressures cease to be able to coexist in the solid frame. Figs. 

 15, 16, 17 and 18, represent the laminar systems resulting from 

 the triangular prism, the hexahedral prism, the tetrahedron and 

 the pyramid with a square base, these systems being supposed 

 to be complete. They are all formed of plane layers, com- 

 mencing at each of the metallic wires ; and that of the hexahe- 

 dral prism, as is shown, contains an additional layer in the centre 

 of the figure. 



35. The system arising from the regular octohedron presents 

 a singular exception, which I have not been able to explain. 

 The layei's of which this system is composed are curved, and 

 form a fantastical group, of which it is difficult to give an 

 exact idea by graphic representations. Fig. 19 exhibits them 

 projected upon two rectangular vertical planes ; and it is seen 

 that the aspects of the system observed upon two adjacent sides 

 are inverse as regards each other. The formation of this system 

 presents a curious peculiarity. At the commencement of the 

 operation, all the faces of the octohedron become simultaneously 



