THE PLANT. 13 



THe elements of this knowledge maybe easily ac- 

 quired, and should be possessed by every person, old 

 or young, whether actually engaged in the cultivation 

 of the soil or not. All are dependent on vegetable 

 productions, not only for food, but for every comfort 

 and convenience of life. It is the object of this book 

 to teach young farmers the first principles of agri- 

 culture : and while it does not contain all that is 

 absolutely necessary to an understanding of the prac- 

 tical operations of cultivation, its teachings are such 

 as the writer found, in his early studies, to be most 

 necessary as a groundwork for future study and 

 thought and most useful in practice. 



We will first examine the atmospheric part of 

 plants, or that wdiich is driven away during combus- 

 tion or burning. This matter, though apparently lost, 

 is only changed in form. 



It consists of one solid substance, carhon (or 

 charcoal), and three gases, ox(/gen, hydrogen and ni- 

 trogen. These four kinds of matter constitute nearly 

 the whole of most plants, the ashes forming some- 

 times less than one part in one hundred of their dry 

 weight. 



When wood is burned in a close vessel, or other- 

 wise protected from the air, its carbon becomes char- 

 coal. All plants contain this substance, it forming 

 usually about one-half of their dry weight. The re- 

 mainder of their atmospheric part consists of the 

 three gases named above. By the word gas, we meai. 

 aeriform matter. Oxygen, hydrogen and nitrogen, 

 when pure, always exist in the form of air. Oxygen has 



