228 CHEMICAL TRANSFORMATIONS. 



these bodies, the compound molecules evidently 

 have different positions in the two forms. In the 

 first form their attraction did not act in the direc- 

 tion in which their power of cohesion was strongest. 

 It is known also, that when sulphur is melted and 

 cooled rapidly by throwing it into cold water, it 

 remains transparent, elastic, and so soft that it may 

 be drawn out into long threads ; but that after a few 

 hours or days, it becomes again hard and crystalline. 



The remarkable fact here is, that the amorphous 

 sugar or sulphur returns again into the crystalline 

 condition, without any assistance from an exterior 

 cause ; a fact which shows that their molecules 

 have assumed another position, and that they 

 possess, therefore, a certain degree of mobility, 

 even in the condition of a solid. A very rapid 

 transposition or transformation of this kind is seen 

 in arragonite, a mineral which possesses exactly 

 the same composition as calcareous spar, but of 

 which the hardness and different crystalline form 

 prove that its molecules are arranged in a different 

 manner. When a crystal of arragonite is heated, 

 an interior motion of its molecules is caused by the 

 expansion ; the permanence of their arrangement 

 is destroyed; and the crystal splinters with much 

 violence, and falls into a heap of small crystals of 

 calcareous spar. 



It is impossible for us to be deceived regarding 

 the causes of these changes. They are owing to a 

 disturbance of the state of equilibrium, in conse- 



