CARBON AND ITS COMPOUNDS. 23 



adding largely to the beauty of the Mineral world. Ob- 

 serve that there is here some analogy to the symmetry 

 that appears in living forms. The two halves of a face, 

 for example, are generally exactly alike, just as are the 

 corresponding parts of a crystal. What the agency is 

 that produces the result is in both cases a wonderful 

 mystery. All that we know is that in the one case the 

 deposition of matter is guided unerringly by a living 

 agency, and in the other by one that is not living. 



CHAPTER III. 



CARBON AND ITS COMPOUNDS. 



I PROCEED now to treat of different kinds of minerals, 

 grouping them according to their natural affinities. 



29. Diffusion of Carbon. As carbon is one of the four 

 grand elements in the composition of vegetable and ani- 

 mal substances, there is a constant interchange in regard 

 to it between the vegetable, animal, and mineral worlds, 

 and therefore it is widely diffused, and appears in vari- 

 ous combinations. Combined with oxygen, it exfcts ev- 

 ery where in the atmosphere in the form of carbonic 

 acid, which is one of the gases that are more or less min- 

 gled or dissolved in the water of the earth. The car- 

 bonates are important salts, the most important being 

 the carbonate of lime, which appears in the various forms 

 of chalk, limestone, and marble, and in the animal world 

 makes the hard covering of shell-fishes and the skeletons 

 of the coral animals. The immense stores of coal laid 

 up in the bowels of the earth is almost wholly carbon. 



30. The Diamond. In strong contrast with the im- 

 mense provision of carbon in the form of coal, this ele- 

 ment is laid up here and there in very small quantities, 

 equally for the use of man, in the most costly and splen- 

 did of gems. That the diamond is pure carbon is proved 



