SECRETARY'S REPORT. 65 



shallow open drains, which lead the water from its natural 

 channel, and keep a constant How, without allowing it to accu- 

 mulate in any part. 



Another kind of irrigation consists in conducting the water 

 into, instead of upon, the land by means of open drains, into 

 which the water can be led and raised sufficiently to saturate 

 the whole area surrounded by the drain. If the field is level, 

 it is sufficient to fill the drain or ditch, and keep it filled till 

 the soil is moistened ; but if the land is sloping, the lower end 

 of the ditch is stopped till the land is saturated, and then let 

 off. It is ordinarily much less expensive than surface irriga- 

 tion, and has been practised with great success in Lombardy, 

 as well as in England and Scotland. This kind of irrigation 

 is more frequently used for cultivated annual crops than for 

 grasses. 



The irrigation of grass lands is found to be very beneficial 

 in moist climates, and in such it greatly promotes the luxuri- 

 ance of the growth. But climate undoubtedly greatly modifies 

 the effects produced. It is the opinion of some that the' grass 

 which has been produced by irrigation is of an inferior quality. 

 This opinion is expressed by several farmers, in answer to the 

 sixth question of the circular, as to the results of experiments 

 in irrigation. This opinion is also expressed by Columella, a 

 celebrated Roman writer on agriculture. " Land/' says he, 

 " that is naturally rich, and is in good heart, does not need to 

 have water set over it; and it is better hay which nature of its 

 own accord produces in a juicy soil, than what water draws 

 from a soil that is overflowed. This, however, is a necessary 

 practice, when the poverty of the soil requires it; and a 

 meadow may be formed either upon a stiff or light soil, though 

 poor when water is set over it. Neither a low field with hol- 

 lows, nor a field broken with steep rising ground, is proper; 

 the first, because it retains too long the water collected in the 

 hollows; the last, because it make3 the water run too quickly 

 over it. A field, however, that has a moderate descent may 

 be irrigated if it be so situated as to admit of it ; but the best 

 situation is where the surface is smooth, and the descent so 

 gentle as to prevent either showers or the rivers that overflow 

 it remaining too long, and, on the other hand, to allow the 

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