AEPINUS A.TOMIZED. 



859 



and the six shown around it in the diagram ; bnt it may be easilj proved 

 that our judgment is not vitiated by the mutual action between the cen- 

 tral quartet and ail aronnd it, including the six in the diagram. Simi- 

 larly we see that any one quartet of the assemblage, free to turn round 

 an axis perpendicular to the plane of the paper while ail the others are 

 fixed, is in stable equilibrium when oriented as are those shown in the 

 diagram. And similarly again we see the same conclusion in respect to 

 three other diagrams in the three other planes parallel to the faces of 

 the tetrahedrons or corresponding octahedrons of the assemblage. Hence 

 we conclude that if the axial constraints are ail removed, and the quar- 

 tets left perfectly free, every one of them rests in stable equilibrium 

 when oriented either as one set or as the other set of equilateral tetrahe- 

 dronal quartets of the assemblage. It is interesting to remark that if, 

 after we turned the central quartet through 60°, we had held it in that 

 position and left ail the others free to rotate, rotational vibrations would 

 have spread out among them from the centre; and, after losing in waves 

 spreading through ether outside the assemblage the energy which we 

 gave them by our torque acting on the central quartet, they would come 

 to stable equilibrium with every one of them turned 60° in one direc- 

 tion or the other from its primitive position, and oriented as the central 

 quartet in the position in which we held it. 



§ 41. We have tlius found that an equilateral homogeneous assem- 

 blage of atoms each having four electrions within it, arranges thèse 

 electrions in equilateral quartets ail oriented in one or other of two 

 ways. The assemblage of atoms and electrions thus produced is essenti- 

 ally octo-polar. Of the two elementary structural tetrahedrons, of the 

 two orientations, one will have every one of its electrionic quartets 

 pointing towards, the other from, its faces. The elementary structural 

 octahedron lias four of its faces pointed towards, and four pointed from, 

 by its electrionic quartets. This is essentially a dynamically octo-polar ') 



*) The octo-polar py ro-electricity , which is supposée! to have been proved by 

 Hauy's experiment, must have been due to something aeolotropic in the heating. 

 Uniform heating throughout a regular cube or octahedron could not give op- 

 posite electric manifestations in the four pairs of alternate corners of the cube, 

 'or alternate faces of the octahedron. Nevertheless the irregular fmding of elec- 

 tric octo-polarity by Hauy is a splendid discovery ; of which we only now 

 know the true and full significance, through the expérimental and mathema- 

 tical labours of the brothers Curie, of Friedel, and of Yoigt. 



