384 EFFECT OF lERIGATION. 



of grass, was undoubtedly suggested by observing the 

 wonderful effects arising from the overflow of rivers. 

 Remarkable examples of this are familiar to many, as 

 the annual or periodical overflowing of the Nile, where 

 the water, without being left to stagnate upon the sur- 

 face, is moving gently over it, depositing whatever allu- 

 vial matter it may hold in suspension. The extraordi- 

 nary richness of the valley of the Mississippi, and on a 

 smaller scale of the valleys of the Connecticut and other 

 rivers, is mainly due, also, to this kind of irrigation ; and 

 this is imitated in our attempts to conduct water over 

 grass land by a system of shallow, open drains, which 

 take the water from its natural channel, keeping a con- 

 stant flow, without allowing it to accumulate in any part. 



The process of surface irrigation is not so simple as 

 many would suppose. It requires considerable skill and 

 practice, and many failures have followed experiments 

 of this kind, made without due care and attention. Sir 

 John Sinclair, however, in speaking of this operation, 

 calls it one of the " easiest, cheapest, and most certain 

 modes of improving poor land, in particular if it is of a 

 dry and gravelly nature. Land, when once improved 

 by irrigation, is put into a state of perpetual fertility, 

 without any occasion for manure, or trouble of weeding, 

 or any other material expense ; it becomes so produc- 

 tive as to yield the largest bulk of hay, besides abun- 

 dance of the very best support for ewes and lambs in the 

 spring, and for cows and other cattle in the autumn of 

 every year. In favorable situations, it produces very 

 early grass in the spring, when it is doubly valuable ; 

 and not only is the laud thus rendered fertile without any 

 occasion for manure, but it produces food for animals 

 which is converted into manure to be used on other 

 lands, thus augmenting that great source of fertility." 



The efi'ect and value of irrigation do not depend 



