Book III. IRRIGATION OF GRASS LANDS. 727 



for the scythe to touch it, whilst that around them, which had been properly watered, would from its 

 luxuriance lie down. Though this method of treating such places is mentioned, their existence ought 

 always to be reprobated ; for every inequality in water meadows should either be levelled down or filled 

 up. Here the irrigator's skill is shown, in bringing the water over those places to which it could not rise 

 of itself, and in carrying it off from others where it would otherwise stagnate. 



4+19. Catch drain is a term sometimes applied to a method made use of to irrigate the land when the 

 water is scarce, and the method is this : when a meadow is pretty long, and has a quick descent, the water 

 i» made to run swiftly down a drain or drains, in which it is stopped at different distances so as to spread 

 it over the adjoining surface. {Seefig. 686. p. 728.) 



4420. The bed of a river, main, trench, &c, is the bottom of it. 



44-1. Pond means water standing upon the land, or in the tail drain, trench drains, &c, so as to injure 

 the ground near them ; and is occasioned sometimes by the flats not having been properly tilled up ; 

 and at other times, when, a ware being shut close, to water some high ground above it, the water 

 is thrown back upon the ground contiguous. In this case the lesser evil, whichever it is, must be 

 borne with. 



4422. A turn of water means so much land in a meadow as can be watered at one time. It is done 

 by shutting down the hatches in all those wears where the water is intended to be kept out, and 

 opening those that are to let the water through. The quantity of land to be watered by one turn 

 must vary with the size of the river, main, &c. as well as with the plenty or scarcity of water. 



44- i The head of a meadow is that part into which the river, main, &c. first enters ; and the tail of a 

 meadow is that part out of which the river, &c. last passes. 



4424. The upper side of a main, or trench, is that side which 'when the main or trench is drawn at, or 

 nearly at, right angles with the river, Sec.) fronts the part whence the river entered. Consequently the 

 lower side is the reverse. 



4425. The upper pane in a meadow is that pane which lies upon the upper side of the main, or trench, 

 drawn at right angles with the river : that is, when the river, &c. runs north and south, entering at the 

 north, and the mains and trenches are drawn east and west, all those panes which lie on the north sie.e 

 of the main, &c. are called the upper panes, those on the south side are called the lower. But it maybe 

 noticed, that where the mains, trenches, &c. run parallel with the river, the panes on either side are not 

 distinguished from each other. 



4426. Meadows are of two sorts : flowing, calculated for a flat country ; and catch-work, 

 for sloping grounds. 



44-7. Flowing meadows. 'Where the ground is flat, the soil is formed into beds, or broad ridges, like 

 those met with at bleachfields. They are commonly from SO to 40 feet wide, and nine or ten poles in 

 length ; as, in such situations, the great object is, when once brought on, to be able to carry off the 

 water quickly. Hence it is necessary to throw up the land in high ridges, with drains between them. 

 More of the failures in irrigation arise from the ridges not being sufficiently high, and the slopes not being 

 sufficiently steep, than from any other cause. {Code.) 



4428. Catch-work meadows. It is diificult to give an intelligible written description of the mode of 

 making these meadows. To be properly understood, the operation must be seen. It may, however, in 

 general be remarked, that the system is calculated for sloping grounds, and that, after the water is brought 

 from the original stream, into a new cut, it is stopped at the end, on as high a level as the case admits of, 

 by which means it is made to fill the trench, and run over at the side, flooding the land below. But as 

 the water would soon cease to run equally, and would wash the land out in gutters, it has been found 

 necessary to cut small parallel trenches, at the distance of from 20 to 50 feet, to catch the water again 

 (hence the name originated), and the same plan of spreading or diffusing is continued, until the water 

 reaches the main drain at the bottom of the meadow. It is a great advantage attending the catch- 

 work system, that it is not only less expensive, but the same quantity of water will do much more 

 work. {Code.) 



Subsect. 3. Preparation of Surfaces for Irrigation. 



4429. Artificial irrigation, Smith observes, is produced by diverting the water of a 

 brook out of its accustomed channel (where there is a fall) in such a manner that, the new 

 watercourse being kept nearly level, the space between the old and new channel may be 

 floated ; the water being brought upon the land by the new channel and taken away by 

 the old one. Thus a constant discharge and succession of water is maintained, without 

 such an accumulation as would make it appear bright upon the land, or without such a 

 deficiency as would leave any part of it not perfectly floating ; for the art of irrigation 

 may be most properly called floating, not soaking nor drowning. Soaking the soiL, 

 similar to the effects produced from a shower of rain, is not sufficient for the general pur- 

 poses of irrigation, nor will damming up water, and keeping it stagnant upon the surface, 

 like that in a pond, or on the fens, produce the desired effect. 



4430. Stagnating water on land may properly be called drowning, because it drowns or 

 covers all the grass, thereby rendering the plants beneath it in some degree aquatic, or 

 the herbage disposed to make such a change ; whereas the herbage of a water meadow 

 should, by the construction and good management of the latter, enjoy the full benefits of 

 both the elements of air and water. Practice has proved that there is no better method 

 of doing this than by keeping water passing over the surface of the land with a brisk 

 current ; not so brisk as to wash away the soil, and yet in sufficient quantity to cover and 

 nourish the roots, but not too much to hide the shoots of the grasses: hence appears the 

 nicety of adjusting the quantity of water ; and hence it also appears, that one main drain 

 to bring the water on the upper side of the mead, and another on the lower side to lake 

 it away, will not be adequate to all the purposes of such an accurate regulation. If the 

 space between the upper channel or main feeder and the lower one or main drain, should 

 therefore be wider than is proper for the good adjustment of the water, that is, so that every 

 part of the space shall have enough water passing over it and no part too much, then that 

 space must be divided into smaller spaces by intermediate drains, which shall catch and 

 re-distribute die water. As the water is brought by the main feeder upon the higher 



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