IRRIGATION. 203 



truth. Is it not admitted, that running waters are 

 alone fit for this purpose ? That after remaining a 

 few days, they are abated, and a new flood must 

 cover the land ? Is not this necessity, of renewing 

 at short periods, the covering of water, which shows 

 no deposit, a proof that it has given up some invisi- 

 ble agent to fertilize the earth ? This invisible agent 

 is oxygen. Is it not evident from the extreme slow- 

 ness with which air is absorbed by water, that, if it 

 were not for the running water, which every few days 

 replaces that which has acted, that the practice of 

 irrigation with pure water could be never success- 

 ful ? 



282. This is the principle, a principle which, 

 having been wholly overlooked, has led to a waste 

 of time and money, and has given to irrigation, in 

 many minds, the odour, if not of a bad, at least, of a 

 useless practice. Where, guided by this light of sci- 

 ence, grass lands can be irrigated, let it be done. If 

 the experience of the most enlightened agricultural- 

 ists in Europe, is not all deception, by simple irriga- 

 tion with running water, the farmer may cut two tons 

 of hay, where he toils and sweats to rake off one. 



283. But by far the most fertile source of increas- 

 ed crops, by irrigation, is found in the impurity of 

 water ; the salts and suspended matter, the slime and 



