IRRIGATION AND WATER STORAGE. 



141 



ing the formation of the land, so as to allow it to soak in 

 without running, which would be more dangerous than in the 

 first instance cited. In cases where the water must be let 

 down to lower levels, in order to do what is necessary 

 that is, saturate the soil catchments or shallow wells 

 (H H) are made, and the overflow water from them used 

 in the still lower parts of the ground. At (c D E F G), 

 while the water is flowing, it is stopped and directed in 

 small streams as required upon the field. 



Irrigating Hill Sides In order to irrigate land thor- 

 oughly, channels or furrows with very little 

 |^i^_^-jr|[ fall for the flow of water have to be laid out 

 by levelling instruments, and by this means 

 gf* ridges and inequalities are saturated by 



1 _" y* ~"~ if carrying the water round their sides, by 

 ^j_= r ~ =H|H contouring. Water gates and sluices, for 

 admitting water from a ditch or other 

 water Gate. channel upon the land to be irrigated, 

 are of various forms. In the gate shown, the flow is 

 regulated by lifting one or more of the pieces of wood 

 which slide between grooves in the side posts, and so 



Irrigating bj Contouring. 



allow the water to flow in, or be stopped, as may be 

 required. 



Where Water is Scarce. Where but smallqtmntilies of 

 water are available, for soakage, the always abundant 

 supply of old fruit and jam tins may be brought into use 

 for home garden irrigation pretty much upon the plan by 

 which Mexicans and Egyptians supply water to plants 



