CRYSTALS. 



279 



How may 



' 



posed by recent fracture, are familiar examples. But 

 where the circumstances are favorable for the forma- 

 tion of individual and separate crystals, the most beau- 

 tiful and symmetrical forms are often the result. 



698. PRODUCTION OF CRYSTALS. Most 



. 



of the salts to be described in this cnap- 

 produced? ter may be 0^^ j n tne form of crys- 



tals, by evaporating or cooling their saturated 

 solutions. The method by cooling, has already 

 been described, in the Chapter on Water. In 

 obtaining crystals by evaporation, the solution 

 is to be moderately heated, in a saucer or other 

 vessel. The crystals formed by either method, 

 commonly contain water, which becomes part of 

 the solid crystal, and is called water of crystalliza- 

 tion. 



699. VARIETY OF CRYSTALS. The forms 

 of leaves and flowers are scarcely more va- 

 rious than those of crystals. The latter are, 

 as it were, the flowers of the mineral world, 



as distinctly characterized in their peculiar beauty as 

 the flowers that bloom in the air above them. Even 

 where color fails, the eye of science distinguishes pe- 

 culiar features which often enable it to determine the 

 nature of a substance, from the external crystalline form 



which it assumes. 



1234 5 



How may the 

 variety of 

 crystals be il- 

 lustrated ? 



