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36 OF CARBON. 



the source from which it is derived, the state 

 in which it exists in nature, its character and 

 general attributes. 



In pursuing this plan each subject will as 

 much as possible be confined to its own limits, 

 but in some cases this will be impossible, as 

 the substances about to be considered are so 

 intimately blended the one with the other, as 

 to render a description of the one necessary to 

 the elucidation of the other. 



One substance, which, although a com- 

 pound body composed of two gases, is yet, in 

 its compound state of water, so important an 

 element in the economy of plants, that the 

 changes it undergoes and the functions it per- 

 forms will be considered when speaking of 

 hydrogen, with which it is so intimately con- 

 nected, as to be incapable of separation. 



OF CARBON. 



Carbon, the first and prime necessary of 

 vegetable life, exists abundantly in nature in 

 three or four states. First, it is a component 

 part of the atmosphere surrounding the globe, 

 one thousand parts of which contain three 

 parts of this gas. In this state it is known as 

 carbonic acid gas, that is carbon united with 

 oxygen gas, and it is one of the most univer- 

 sally diffused substances in nature. It exists 

 in another state, as charooal, which is almost 

 pure carbon, and lastly, in the diamond, whicli 

 is pure carbon in its crystalline state. 



