AGRICULTURAL DRAINING. 



41 



necessary to make temporary shelter, we are looking 

 forward to the house in prospective, which can be made a 

 home in the best sense of the term. 



~ . 



Barren until Drained. 



IV. AGRICULTURAL DRAINING. 



To see that the drainage of his land is right is 

 amongst the most important matters the agriculturist 

 has to deal with. It is all important in warm, semi- 

 tropical countries, subject to 

 excessive falls of rain, and to 

 spells of parching drought. In 

 a sentence it might be said that 

 soil to be of its true value to 

 the cultivator should be porous 

 to the depth of from two to 

 four (eet, to admit water to 

 filter through it, and with free 

 egress for any surplus rain, so 

 that no water can rest or 

 accumulate in the surface soil, 

 or the subsoil reached by the roots of cultivated crops. 

 When water saturates a soil, its first effect is to expel the 

 air which it contains and the gases which may have been 

 generated in it. But as the water moves 

 along in the soil, as from D to c to A, and 

 into the drain, it is followed by fresh 

 atmospheric air, the oxygen in which at 

 once stimulates into activity important 

 chemical changes, furnishing a fresh 

 supply of food for plants. There are 

 some subsoils naturally porous, and which 

 admit the water to pass downwards and How Soil is Deepened . 

 drain off; but the majority of subsoils are 

 tenacious ; and in land which abounds in iron, hard cement- 

 like layers are formed. These layers prevent water and 

 the roots of plants from penetrating, although there may 

 be rich material below. When rain falls, the shallow 

 surface is soon saturated, and is either washed into ruts or 



