Mr. J. F. Daniell on Crystallization. 37 



parallel, and their shortest diameters in the same plane. The 

 manifest consequence of this structure would be, that a solid 

 so formed would be liable to split into plates at right angles 

 to its axis, and the plates would divide into prisms of three or 

 six sides, with all their angles equal ; as occurs in phosphate of 

 lime, beryl, &c. 



It is, however, a very singular circumstance, that the con- 

 struction of the cube with spheres, upon the same principle as 

 the octohedron and the other solids of that series, escaped the 

 ingenious author of this hypothesis a failure which, had it 

 been essential, instead of accidental, would have rendered it as 

 untenable as that whose defects it was intended to supply. 



Dr. Wollaston was perfectly aware that the hypothesis must 

 have appeared defective, if it had not included some view of 

 the manner in which so simple a form might originate ; the 

 only mode which occurred to him of supplying this desidera- 

 tum was, to imagine a mass of matter to consist of spherical 

 particles, all of the same size, but of two different kinds, in 

 equal numbers, represented by black and white balls : these, he 

 suggested, might be arranged four and four above each other, as 

 in the following figure, alternately black and white throughout : 

 the distances of the centres of the black balls, being every way a 

 superficial diagonal of the cube, are equidistant, and their con- 

 figuration represents a regular tetrahedron ; and the same is the 

 relative position of the four white balls. Every black ball is 

 thus equally distant from all surrounding white balls, and all 

 adjacent balls of the same denomination are also equidistant 

 from each other, and the whole might be conceived to be in 

 equilibrio. 



The experimental part of the investigation had hitherto been 

 confined to the action of mechanical force ; by the application 



