6q Dr. WoLLASTON on the elementary Particles 



must be regarded as favourable to the foregoing hypothesis, 

 haniely, that many of those substances, which we have most 

 reason to think simple bodies, as among the class of metals, 

 exhibit this further evidence of their simple nature, that they 

 crystalline in the octohedral form, as they would do if their 

 particles were spherical. 



But it must, on the contrary, be acknowledged, that we can 

 at present assign no reason why the same appearance of sim- 

 plicity should take place in fluor spar, which is presumed to 

 contain at least two elements ; and it is evident that any at- 

 tempts to trace a general correspondence between the crystal- 

 lographical and supposed chemical elements of bodies must, in 

 thie present state of these sciences, be premature. 



Note, A theory has lately been advanced * by M. Prechtl 

 which attempts to account for Various crystalline forms from 

 the different degrees of compression that soft spheres may be 

 supposed to undergo in assuming the solid state. It is sup- 

 posed, that with a certain degree of softness liiid of relative 

 attraction, the particles will be surrounded each by four others, 

 and will all be tetrahedral, although in fact it be demonstrably 

 impossible that tetrahedrons alone should fill any space. 



It is next supposed, that soft spheres less compressed will 

 be surrounded by five others, and will be formed into trian- 

 gular prisms, comprised under five similar and equal planes. 

 That they should be similar is impossible, and it is further 

 demonstrable, that when the triangular termination of such a 



• Journal des Mines, No. i6d; 



