156 Xahiral Histoi^. [CiLtp. LH. 



takes place in this instance to be produced by the 

 attraction w hich he had proved to exist between 

 the particles of all bodies, and which acts as soon 

 as these particles are brought within a certain 

 distance of each other by the evaporation of the 

 Jiq«id in which tlw^y are dissolved. The regularity 

 of their figure he explained, by supposing that, 

 while in a state of solution, they were arranged in 

 the liquid in regular rank and file ; the consequence 

 of which, as they ^re acted upon by a power which 

 at equal distances is equal, and at unequal distances 

 ■unequal, will be crystals of determinate figures. — 

 Thie explanation, which is worthy of the luminous 

 and acute mind of its author, is now generally ad- 

 mitted as the true one, and has contributed much 

 towards the elucidation of the subject. 



Still, however, there remained various pheno- 

 mena respecting crystallisation, which required to 

 "be more fully explained. To effect this, many at- 

 tempts have been made, and several theories form- 

 ed. — Rome de Lisle professed to have determined 

 -the j^rimitive form of every crystallised substance, 

 and to have ascertained that all other forms arc 

 only modifications of this. — Gahn, of Sweden, w^ent 

 further. I laving broken a calcareous spar of a par- 

 ticular kind (dog-tooth), he found that the crystal 

 was entirely composed of small rhombs, like those 

 of the primitive calcareous spar. — Bergman seized 

 npon 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 

 ease, according to certain laws of decrement. 

 These little elementary crystals are called by him 



