HAPPY INDIA 169 



drainage canals, so that the fields do not get water- 

 logged, the ground is not turned into a swamp. 

 Wherever this drainage is not properly carried out, 

 the ground gets eventually water-logged and seriously 

 injured. 



Practically all river water contains some salts 

 of various kinds. These salts get into the river 

 water, because the rain on the hills and mountains, 

 the little streams, the swamps, pools and lakes 

 dissolve these salts out of the soil, sands and rocks. 

 The river carries the salt down to the sea, and every 

 year the sea gets more salt. 



In large districts of the Ganges plains where 

 irrigation canals have been introduced and freely 

 used, the ground has been poisoned because the 

 system of drainage has been defective. A great 

 deal of the irrigation waters sink down into the 

 ground, and gradually the subsoil water-level rises 

 until it gets within, say, 3 feet of the surface. Then 

 in the summer time the water rises by capillary 

 channels up to the surface, and there is evaporated 

 by the great heat of the sun. The mineral contents 

 of the water are left on the top of the ground. There- 

 fore, if this capillary attraction goes on year after 

 year, and the water is evaporated and the minerals 

 deposited, there gradually gets so much salt on the 

 surface that the ground becomes incapable of giving 

 good crops. 



In other cases, as a result of free irrigation, the 

 ground becomes actually swampy, and in India 

 swamps are the cause of malaria, because the mosquito 



