of certain Crystals. 61 



white throughout. The four black balls are all in view. The 

 dii^tances of their centres being every way a superficial diago- 

 nal of the cube, they are equidistant, and their configuration 

 represents a regular tetrahedron ; and the same is the relative 

 situation pf the four white balls. The distances of dissimilar 

 adjacent balls are likewise evidently equal ; so that the con- 

 ditions of their union are complete, as far as appears in the 

 small group : and this is a correct representative of the entire 

 mass, that would be composed of equal and similar cubes. 



Since the crystalline form and electric qualities of boracite 

 are perhaps unique, any explanation of properties so peculiar 

 can hardly be expected. It may, however, be remarked, that 

 a possible origin of its four pair of poles may be traced in the 

 structure here represented ; for it will be seen that a white 

 ball and a black one are regularly opposed to each other at 

 the extremities of each axis of the cube. 



An hypothesis of uniform intermixture of particle with par- 

 ticle, accords so well with the most recent views of binary 

 combination in chemistry, that there can be no necessity, on 

 the present occasion, to enter into any defence of that doctrine, 

 as applied to this subject. And though the existence of ulti- 

 mate physical atoms absolutely indivisible may require de- 

 monstration, their existence is by no means necessary to any 

 hypothesis here advanced, which requires merely mathemati- 

 cal points endued with powers of attraction and repulsion 

 equally on all sides, so that their extent is virtually spherical, 

 for from the union of such particles the same solids will re- 

 sult as from the combination of spheres impenetrably hard. 



There remains one observation with regard to the spherical 

 form of elementary particles^ whether 3 ctual or virtual, that 



