DRAINAGE AND IRRIGATION. 43 



ences of its rest, planting may be successfully com- 

 menced. 



The greatest difficulties in restocking denuded wood- 

 lands are encountered on the bare, steep slopes of the 

 mountains, because every heavy rain carries away from 

 there a part, if not every particle of the soil. Help 

 against this trouble is found in seeding the places with 

 quick growing, and, as to plant-food, unpretentious 

 grasses, or planting such trees as will by their nets of 

 roots bind the soil. On this mode of culture we shall 

 treat in Part III. 



CIIAPTEE IX. 

 DRAINAGE AND IRRIGATION. 



The supply and the preservation of water in the 

 soil is of the greatest importance to the growth of trees. 

 Wherever drainage is required, there should at the same 

 time be considered the question of preserving the humi- 

 dity in the ground. By lowering the water table — i. e., 

 the top of the ground water, we always must prevent the 

 exsiccation of the soil, if necessary, by the erection of 

 some apparatus for stopping the flow of water at any do- 

 sired time. 



A proper quantity of humidity in the soil always exer- 

 cises a beneficial effect upon the growth of trees, the 

 roots of which only being able to assimilate the plant food 

 contained in the soil, after this has been made liquid by the 

 water. But stagnant water is detrimental to the growth 

 of every vegetation : it kills the activity of the roots. In 

 order to retain the proper degree of moisture in the 

 soil of the plains, there should not only be had regard 

 to the humidity received from the atmosphere, but 

 also to the water contained in the subsoil, the ground 

 water. The less rain is falling in the country, and the 



