144 OUTLINES OF FORESTRY. 



must have existed in the air in enormous quanti- 

 ties ; for, the vast deposits of carbon, which form 

 the coal-beds now found in the different parts of 

 the crust, then existed in a gaseous condition in 

 the atmosphere combined with oxygen. 



Animal life of the present type was impossible 

 in the unpurified atmosphere that existed before 

 the Carboniferous age. The conditions were, how- 

 ever, such as to favor dense and luxuriant plant 

 life, and at no time in the world's history, either 

 before or since, has such luxuriant vegetable 

 growth existed. 



A twofold action of purification was effected by 

 the plants of the Carboniferous period ; namely, 

 the separation of the carbon and the liberation of 

 the oxygen. 



The exact balance between the plant and ani- 

 mal life of the earth, so carefully established 

 by nature, cannot be disturbed without marked 

 changes in the entire races of animals and plants 

 that now exist. 



The thoughtless and unnecessary removal of the 

 forests from over extended areas will not only dis- 

 turb the balance during the time such surfaces are 

 bare, but since, in many cases, such removal per- 

 mits this section of country to be denuded of its 



