AMELIORATION OF LAND 83 



a field of this character in such a way. It 

 will be much cheaper and quite as effective 

 to sink, what is called, a " catch r drain 

 close along the level where the water is found 

 to be rising to the surface, and by this means 

 to intercept the water before it gets on to 

 the field lying at a lower level. 



It is not proposed to discuss the technical 

 details of the practice of draining, which can 

 best be learned from a practical surveyor, 

 assisted by reference to a reliable text-book. 



An ameliorative process, which in some 

 respects is the exact opposite of drainage, is 

 irrigation, that is to say, the leading of 

 water on to land in place of off it. This 

 process is capable of application only under 

 somewhat limited circumstances. In the first 

 place it presupposes a supply of water in 

 sufficient quantity and of suitable quality. 

 Moreover, irrigation is only successful upon 

 land of somewhat special character. Very 

 indifferent results are obtained by leading 

 water on to land that is so stiff and im- 

 pervious as to prevent the water filtering 

 through the mass. To obtain good results 

 the land must be sufficiently porous to permit 

 of a large amount of percolation, although it 

 is not suggested that all the water led on to 

 a field should escape only by the subsoil 



