Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/381

365 the case, then the crowns should be made towards the upper sides, more or less according to the lateral slope of the ground. The crowns should rise a foot above the adjoining furrows. The beds thus formed should slope in an inclined plane from the conductor to the main drain, that the water may flow equably over them. The beds are watered by "feeders," that is, channels gradually tapering to the lower extremities, and their crowns cut down, wherever these are placed. The depth of the feeders depends on their width, and the width on their length. A bed 200 yards in length requires a feeder of 20 inches in width at its junction with the conductor, and it should taper gradually to the extremity, which should be 1 foot in width. The taper retards the motion of the water, which constantly decreases by overflow as it proceeds, whilst it continues to fill the feeder to the brim. The stuff which comes out of the feeders should be carefully and evenly laid along the sides of the beds. The water overflowing from the feeders down the sides of the beds is received into small drains formed in the furrows between the beds. These small drains discharge themselves into the main drain, and are in every respect the reverse of the feeders ; that is, their tapering extremities lie up the slope, and their wide ends open into the main drain, to accelerate the motion of the departing water. The depth of the small drain at the junction is made about as great as that of the main drain, and it gradually lessens towards the taper to 6 inches in tenacious and to less in porous soils. The depth of the feeders is the same in relation to the conductor. The stuff obtained from the small drains is employed to fill up inequalities in the meadow. For the more equal distribution of the water over the surface of the beds from the con ductor and feeders, small masses, such as stones, or solid portions of earth or turf fastened with pins, are placed in them, in order to retard the momentum which the water may have acquired. These "stops," as they are termed, are generally placed at regular intervals, or rather they should be left where any inequality of the current is observed. Heaps of stones answer very well for stops in the con ductor, particularly immediately below the points of junction with the feeders. When tough pieces of turf are used, care must be taken to keep the tops of the pins below the reach of weeds floating on the surface of the water. These stops, however, are nothing but expedients to rectify work imperfectly executed. It must be obvious that a perfectly formed water-meadow should require few or no stops. The small or main drains require no stops. The descent of the water in the feeders will no doubt necessarily increase in rapidity, but the inclination of the beds and the tapering of the feeders should be so adjusted as to counteract the increasing rapidity. At all events notches cut into the sides of the feeders to retard the velocity of the water are much more objectionable than stops, although some recommend them. The distribution of the water over the whole meadow is regulated by the sluices, which should be placed at the origin of every conductor. By means of these sluices any portion of the meadow that is desired can be watered, whilst the rest remains dry ; and alternate watering must be adopted when there is a scarcity of water. All the sluices should be substantially built at first with stones and mortar, to prevent the leakage of water ; for, should water from a leak be permitted to find its way into the meadow, that portion of it will stagnate and produce coarse grasses. In a well-formed water-meadow it is as necessary to keep it perfectly dry at one time as it is to place it under water at another. A small sluice placed in the side of the conductor opposite to the meadow, and at the upper end of it, will drain away the leakage that may have escaped from the head sluice. To obtain a complete water-meadow, the ground will often require to be broken up and remodelled. This will no doubt be attended with cost ; but it should be considered that the first cost is the least, and remodelling the only way of having a complete water- meadow which will continue for years to give satisfaction. To effect a remodelling when the ground is in stubble, let it be ploughed up, harrowed, and cleaned as in a summer fallow, the levelling-box employed when required, the stuff from the conductors and main drains spread abroad, and the beds ploughed into shape, all operations that can be performed at little expense. The meadow should be ready by August for sowing with one of the mixtures of grass-seeds already given. But though this plan is ultimately better, it is attended with the one great disadvantage that the soft ground cannot be irrigated for two or three years after it is sown with grass-seeds. This can only be avoided where the ground is covered with old turf which will bear to be lifted. On ground in that state a water-meadow may be most perfectly formed. Let the turf be taken off with the spade, and laid carefully aside for relay ing. Let the stript ground then be neatly formed with the spade and barrow, into beds varying in breadth and shape according to the nature of the soil and the dip of the ground, the feeders from the conductor and the small drains to the main drain being formed at the same time. Then let the turf be laid down again and beaten firm, when the meadow will be complete at once, and ready for irrigation. This is the most beautiful and most expeditious method of making a complete water-meadow where the ground is not naturally sufficiently level to begin with. The water should be let on, and trial made of the work, whenever it is finished, and the motion of the water regulated by the introduction of a stop in the conductors and feeders where a change in the motion of the current is observed, beginning at the upper end of the meadow. Should the ivork be finished as directed by August, a good crop of hay may be reaped in the succeeding summer. There are few pieces of land where the natural descent of the ground will not admit of the water being collected a second time, and applied to the irrigation of a second and lower meadow. In such a case the main drain of a watered meadow may form the conductor of the one to be watered, or a new conductor may be formed by a prolongation of the main drain ; but either expedient is only advisable where water is scarce. Where it is plentiful, it is better to supply the second meadow directly from the river, or by a continuation of the first main conductor. In some instances it may be necessary to carry a conductor over a hollow piece of ground along an aqueduct made for the purpose, called a "carry- bridge. " Such an aqueduct may be made either of wood, cast-iron, or stone and mortar ; or inverted siphons may be used. Catchivork Irrigation. In the ordinary catch work water-meadow, the water is used over and over again. On the steep sides of valleys the plan is easily and cheaply carried out, and where the whole course of the water is not long the peculiar properties which give it value, though lessened, are not exhausted when it reaches that part of the meadow which it irrigates last. The design of any piece of catchwork will vary with local conditions, but generally it may be stated that it consists in putting each conduit save the first to the double use of a feeder or distributor and of a drain or collector. The following description of one of the best ways in which a catch- work meadow plan may be constructed is condensed from Mr Bickford s account in the Journal of the A . Agric. Soc., 1852. This comparatively cheap system, though at first chiefly used on the sloping sides of Devonshire and Somersetshire valleys, has been successfully applied to level meadows. In one case the fall was but 1 in 528. "This system has the advantage over the common system of obviating the necessity for large and frequent level gutters ; it has the effect of continuing (and even causing) a smooth and uniform surface to the meadow, allowing of the operations of mowing and carting without any sensible perception of the existence of the gutters ; and also that of accelerating the speed of the water over the land when turned on, and the speedily draining the water from the surface when turned off. It becomes a ready instrument in the hands of the irrigator, and obviates that waste of land occasioned by the usually large gutters. It is every way better than the old system : it can be done in half the time, and for less than half the expense. The chief features of the system consist in causing the ground intended to be irrigated to be covered with a network of small gutters, intersecting each other as nearly at right angles as circumstances will permit. These gutters are about 4 inches wide and 1 inch deep ; they are cut with a die, fixed in a sort of plough of simple construction, drawn generally by one horse. This network of gutters is fed at the highest level possible, or thought desirable, by a carriage gutter of sufficient size. " Let fig. 1 be a piece of meadow ; look first where the water enters the meadow, or where it can best be made to enter. Let this be ascertained to be at A 1. Then estimate roughly where it may be supposed the water will run, say, along the dotted line 1 .... 2. Next proceed, using a simple level adjusted by means of a plumb-line, to lay down a level line made across the meadow, such as BC. The arrows marked on the line show the way the B water is to be made to run on in the D gutter line, to ob tain Avhich it is necessary to deviate from precise level- L ling, and allow the plumb-line to drop I a little before the ,-,. level mark when in clining down, and a little behind it when inclining up the meadow. This will have the effect of running the water out of the low places, and upon the high places. Care must be taken in levelling to follow out the indications of the level, however crooked and curved the line may appear, going down around every elevation, and avoid ing every disposition to cut the line straighter. " Having completed that line, return to the side first begun, say to D, about 10 paces down from B ; and by proceeding as in BC the line DE will very likely be produced. Should C and E be too far asunder, begin again at F, and produce the line FG. The middle of the meadow is supposed to be lowest, and the meadow itself to be flat, rising on each side of the middle by two gentle Aj-