IRRIGATION AND DRAINING. 79 



CHAPTER IV. 



IRRIGATION AND DRAINING. 



IRRIGATION may properly enough be classed under the 

 head of manures; as the materials which it provides are 

 not only food for plants, but they aid also in procuring it 

 from other sources. Water is of indispensable necessity to 

 vegetable life ; and the great quantity of it demanded for 

 this purpose, is in most climates, amply provided by nature 

 in the stores of rain and dew which moisten the earth, and 

 especially during the early growth of vegetation, when it is 

 most required. In countries where rain seldom or never 

 falls, as in parts of South America, Egypt, and elsewhere, 

 the radiation of heat from the surface, is so rapid under their 

 clear skies, that excessive deposites of dew, generally supply 

 the plants with all the moisture which they need. The 

 same effect takes place in our transparent, summer atmos- 

 phere, throughout most of the United States ; and it is to 

 the presence of copious dews, on our rich, well cultivated 

 fields, that much of the luxuriance and success is due, 

 which has ever attended enlightened and judicious American 

 husbandry. 



Besides the moisture that abounds in the atmosphere, (but 

 which is not always available in rains and dews to the 

 extent desired for the wants of vegetation), and that wixich 

 imperceptibly ascends from remote depths in the earth, and 

 contributes to the support of plants ; it is a practice coeval 

 with the earliest history of agriculture, to bring artificial 

 waters upon the cultivated fields and make them tributary 

 to the support of the crops. In many countries this, sys- 

 tem is indispensable to secure their maturity ; for although 

 dews accomplish the object in a measure, they do not sup- 

 ply it in the quantity required to sustain a vigorous growth. 

 We find, in looking to the practice of Egypt and the Barbary 

 States in Africa ; of Syria, Babylon, and other parts of 

 Asia ; Italy, Spain and elsewhere in Europe, in each of 

 which, husbandry early attained a high rank, that irrigation 



