120 Additional Notes. 



gular rank and file; the consequence of which, as they arc 

 acted upon hy a power which at equal distances is equal, and 

 at unequal distances unequal, will be crystals of determinate 

 figures. — This explanation, which is worthy of the luminous 

 and acute mind of its author, is now generally admitted as 

 the true one, and has contributed much towards the elucida- 

 tion of the subject. 



Still, however, there remained various phenomena respect- 

 ing crystallization, which required to be more fully explained. 

 To effect this many attempts have been made, and several 

 theories formed. 



Rome de Lisle professed to have determined the primi- 

 tive form of every crystallized substance, and to have ascer- 

 tained that all other forms arc only modifications of this. — 

 See his CnjstaUographie. 



Gahn, of Sweden, v^'cnt further. Having broken a cal- 

 careous spar of a particular kind (dog-tooth), he found that 

 the crystal was entirely composed of small rhombs, like those 

 of the primitive calcareous spar. 



Bergman seized upon this idea of his pupil; and as he 

 combined an attention to geometry with physical science, he 

 demonstrated that every crystal is composed of other small 

 crystals, variously piled, but, in each case, according to cer- 

 tain laws of decrement. These little elementary crystals are 

 called by him constituent parts of a ciysial. In this manner 

 Bergman developed the mechanical structure of various 

 crystals, and showed that the primitive form often lies con- 

 cealed in those very crystals which appear to deviate farthest 

 fi-om it. 



M. Hauy pursued the idea, and applied it to various crys- 

 tallized minerals. He is supposed to have shown, not only 

 that every particular species of crystal has a primitive figure, 

 and that the variations are owing to the different ways in 

 which the particles arrange themselves; but also to have de- 

 termined the laws according to which the decrements take 

 place, after certain data which he assumed. His theory of 

 crystallization has been much celebrated. It is generally con- 

 sidered as ingenious and plausible; and certainly manifests a 

 degree of diligence, zeal, and mathematical skill, which en- 

 title him to much commendation. — See Tilloch'^ Philoso- 

 phical Magazine, 1<1 icholso-n' s Journal^ and also a good 

 abstract of Hauy's system in the Supplement to the Ency- 

 dopcedia Britannica. 



