CHAP. xii. MODE OF WATERING MEADOWS. 877 



of the Nile by means of machines which they worked with their 

 feet, and poured it over their fields in places to which the inundation 

 did not reach, or in seasons of the year when, in that hot country, 

 water was necessary to the continuance of vegetation. These sakias 

 still exist. The Greeks and Romans also practised various methods 

 of watering their fields, as is evident from passages in the writings of 

 Virgil, Cato, Columella, and Pliny. At the present day, in Southern 

 Asia, the watering of land from rivers and brooks, and, if no better 

 source can be obtained, from wells, is essential to the support of the 

 inhabitants. In every part of southern Europe the water is conveyed 

 in little channels to the corn-fields, the vineyards, and the olive-trees. 

 In the western portions of the United States, as well as in parts of 

 Australia, irrigation is rapidly increasing in favour. 



The system of irrigation practised in Britain may, in a very few in- 

 stances, be intended to supply the natural deficiency of moisture in the 

 soil ; but, generally speaking, a different purpose is to be answered. The 

 water flows over the meadow at seasons when there is already a supply 

 of moisture. It flows over it, but is not permitted to stagnate upon it, 

 or the plants would be rendered in some degree aquatic. It often 

 apparently contains no fertilising material. There is no rich mineral 

 sediment. It merely flows over the land for a while, and is then 

 carried off as quickly as it entered, and many persons are inclined to 

 attribute the beneficial effects resulting from irrigation simply to the re- 

 freshing influence of the current ; while others, on the contrary, conceive 

 that the water contributes warmth to the soil and thus benefits it ; but 

 more scientific reasoners consider that irrigation is most fertilising 

 where the chemical ingredients held in solution by the water are such as 

 most readily affect the component parts of the soil. Pure water is 

 seldom so beneficial in its action as water which is impregnated with 

 organic or earthy matter. Certain it is that these considerations have 

 not hitherto been sufficiently attended to, or it would have ceased to 

 be a problem why irrigation should be so successful in one place and 

 such a failure in another. 



The ordinary mode of watering meadows may be briefly described. 

 Suppose a stream of water lying contiguous to and somewhat lower 

 than a river, adjacent to the field to be watered : a dam is thrown 

 across the stream, or a sluice is dug in the bank, communicating with 

 a channel or head main in the highest part of the field, which is filled 

 with the water until its banks overflow. From this there run certain 

 trenches, or small mains, called carriers or carriages ; these are filled 

 until they run over throughout the whole length. Drains are made in 

 the lowest part of the meadow, as nearly parallel with the small drains 

 as possible ; the purpose of which drains is to discharge the water into 

 a tail or main drain, which conveys it off the meadow. 



In order to make the water run uniformly over the sides of the 

 trenches, stops are placed in them at proper distances, which, by 

 obstructing the course of the water, cause it to rise a little and over- 

 flow the neighbouring ground to a greater or less extent. These stops 

 are formed by laying across the trench pieces of turf, which reach as 



