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but also to preserve them from being overflowed by any other water that might come down upon them from higher ground. On this account* it will be necessary to allow any rivulets that may flow through these, to fall into the river without any obstruction; banks of the same kind being continued along each side of these as far as the haugh-ground extends. And, if the back part of these haughs, where it borders with tthe higher ground, be bounded with a good ditch to in-f tercept the water that may fall from it, with openings at proper places into the river, they will be effectually secured from all extra-, neoua water whatever, and remain quite dry, while the water all around them is higher than the surface of the ground in them, if the possessor (hall so incline.
To illustrate this more distinctly, I have subjoined the plan of a small part of a river, with haughs on each side of it, secured in this manner (at Fig. 17th), in which AB re-*
present* presents the river secured by its bank on each fide ; C and D, rivulets that fall into it, confined by banks on each side of them, as far as is necessary; EFG is the ditch that separates the low from the high ground; which receiving the water that descends from the heights carries it in the direction EF, till it falls into the rivulet upon the one side; and, on the other side falling towards G, it flows on till it comes to some other part, where it may be found necessary to make an opening for it into the river. The lines H, I, K, are the dikes dividing the haugh into fields of a moderate extent, which may be nearer or farther from one another as the field has more or less declivity. These dikes ihould be of a considerable thickness, and may be formed of the earth taken from a ditch on each side thereof, (as at Fig. 19th,) which ditch should be carried quite round each of the fields, in order to receive and
Offreeing the Fields^ thus fenced^ from Water that might arise from Springs uuithin thefame.
But, it is not only necessary thus to secure our fields from being hurt by water from the river or higher ground, but also, to provide an outlet for the water that may be within them. For, unless such outlet be provided to carry off the superfluous water that may fall upon these fields from the clouds, or rife from springs within them, our improvement would be very imperfect. On this account, it will be necessary to be attentive, when forming the bank, to leave a
small small conduit at the lowermost corner of each field, as is represented by the dotted lines L, L, L, L. Each of these should be carried quite thro' the bank from the ditch L, (Fig. 14th,) as represented by the dotted lines L, H, and should be built of solid mason-work, well rammed at the back with soft clay, to render it quite impervious to water. At L, (Fig. 14th,) there should be formed a close water-sluice that could be opened or shut at pleasure; and, on the other end of the conduit, at H, there should be a wooden door with the hinges upon its upper-fide, so as to make it open with its back towards the stream; by which means, when the water of the river rises above the level of the line LH, it will press upon the back of the door, so as to shut it, and prevent the water from flowing into the field at that time ; and, when the river again falls to its ordinary level, the door will be easily forced up by the pressure of the water from within, if there
has been any accumulated there during the time of the inundation, and it will be allowed to fall easily into the river.
This kind of fluice is well known, and
. has been frequently described; but, as it. is difficult to get them made to close so exactly as to admit of no water at all, I have directed to employ likewise the inner-sluice at L, which could be made to shut more accurately, and could be closed upon extraordinary occasions; and the folding fluice would be of use to keep out a good deal of the water when the inundation happened in the nighttime, or so suddenly as to be pretty high before the farmer could have time to get the innersluice stopped. The inner-sluice alone w ould be entirely sufficient, unless where there happened to be springs within the field; which being kept in general shut, could be opened
. when occasion might require.