18 THE PKLXCIPLLS OF AGRICULTURE. 



Organic substances arc those Avliicli have been con- 

 verted into living" organisms ; or, in other words, which 

 either form or luive formed a part of the bodies of 

 plants and animals. They are produced by the; processes 

 of life. All other matter is called inorganic;. 



When organic matter is burned or decays, it returns 

 again to an inorganic conditi(jn. 



Pieces of stone or iron, for instance, are not organic, 

 because they have no organs such as exist in anything 

 which has life. On the other hand, wood, hay, flesh, 

 and bones are examples of organic matter, since they 

 have been produced by the growth of living plants and 

 animals, and retain the same matter and the same form 

 which they had when in a living state. Soil may be 

 partly organic and partly inorganic, since it not only 

 contains mineral matter, but also vegetable and animal 

 matter, left by the death of plants and animals, which 

 has not yet become so far changed as to lose its organic 

 condition. 



Organic substances have never been produced by arti- 

 ficial means. For articles of food, — fruit, vegetables, 

 and meat, — as well as for the materials used for cloth- 

 ing, — cotton, wool, linen, and silk, — the world must 

 depend upon nature's processes in agriculture. 



All attempts to imitate nature by producing these sub- 

 stances have failed. 



Combustible and Incombustible Matter. — When any sul)- 

 stanee is burned, some of its elements esca|)e into the 

 at]n()Si)here in the form of gases and floating jiarticles, 

 and the remainder become ashes. The carbon unites 

 with the oxygen of the aii-, and escapes as carbonic acid 

 gas. Some of the nitrogen is converted into ammonia 

 gas. The water is converted into vapor. 



