THE EFFECT OF DRAINING. 121 



sinking a hogshead, or, more permanently, by build- 

 ing a small reservoir of brick or stone. The drain 

 above leads into it, and the one below takes off the 

 surplus water. These are very convenient for use 

 in the orchard, and in furnishing the workmen with 

 cool water. They are also interesting, as they show 

 the operation of the drains. 



7. The discovery of ohstructions. All drains will 

 sometimes become stopped, either by some animal 

 which has taken refuge in the pipe, or by sediment. 

 When such is the case, and the ground is wet, the 

 point can generally be detected by the external 

 appearance of the land. On a slope, the water will 

 often burst forth upon the surface. When this does 

 appear, the tile must be taken up at the obstructed 

 part and cleaned. Over drains from which there is 

 a continual flow of water, no crop should be planted 

 whose roots will be attracted by it so as to fill up 

 and choke the pipe ; but there is no danger of this 

 over those whose flow is confined to the wet season, 

 and after heavy rains. 



We have now considered the sources of moisture 

 in the soil, and the means of removing it, and thus 

 are prepared to notice the eff'ect produced. 



It promotes pulverization. The comminution of 



the soil is of great importance, as it permits the 



free entrance of the air among its particles. Indeed, 



of so much value is this pulverization of the ground, 



11 



