CRYSTALLOGRAPHY. 



1. CRYSTALLIZATION OF MINERALS 

 CRYSTALLOGRAPHY. 



1. General Remarks on Crystallization. 



The attraction which produces crystals is one of the funda- 

 mental properties of matter. It is identical with the cohesion 

 of ordinary solidification ; for there are few cases outside of the 

 kingdoms of life in which solidification takes place without some 

 degree of crystallization. Cohesive attraction is, in fact, the 

 organizing or structure-making principle in inorganic nature, it 

 producing specific forms for each species of matter, as life does 

 for each living species. A bar of cast-iron is rough and hackly 

 in surface, because of the angular crystalline grains which the 

 iron assumed as solidification took place. A fragment of mar- 

 ble glistens in the sun, owing to the reflection of light from in- 

 numerable crystalline surfaces, every grain in the mass having 

 its crystalline structure. When the cold of winter settles over 

 +he earth in the higher temperate and colder latitudes it is th*» 



CRYSTALS OF SNOW. 



aignal for crystallization over all out-door nature ; the air u 

 filled with crystal flakes when it snows ; the streams become 

 coated with an aggregation of crystals call ed ice ; and windows 

 are. covered with frost because crystal has been added to crystal 



