The method of forming and laying out water-meadows will be easily gathered from the following sketch of the different species of irrigation as practiced in this country.
1. method can only be conveniently applied to ground which is nearly level. It consists in laying out the ground into sloping beds or ridges, from 30 to 40 ft. wide, according to the nature of the soil, having their upper ends lying in , gentle slope from one side to the other of the meadow. Along the upper ends of the b,als is drawn the drain or conductor, which brings the water from the reservoir or river, as the case may be; and this conductor must be tapered off towards its further end, in Order that the diminished supply of water may still overflow. From this conductor, small drains, called feeders, are led down along the crown of each ridge. In the lowest part of the meadow, a main-drain, which must be made nearly as large as the conductor, is cut across the lower ends of the beds, and the water, after having served the purpose of irrigation, is led into it by means of small drains cut in the furrows. The feeders should, like the conductor, taper towards their further extremity, both for the purpose of retard ing the velocity of the water, and of preserving a continual overflow along their whole length. On the contrary, the small drains should gradually widen towards their lower extremity, where, they meet the main-drain. The dimensions and inclination of the con ductor and feeders should be so regulated to the water-supply, that the beds can be wholly laid under water to the depth of about one inch. The expense of bed-work irrigation ranges from £20 to £40 per acre.
2. Irrigation differs materially from the former; it can be applied to land whether level or not, costs only £4 per acre, and, in the opinion of many, is quite as effective. The conductor formed as before is led along the highest side of the field, then with the aid of a level, a succession of perfectly level gutters (which, of course, must be winding) are drawn across the field in the same direction as the conductor, and not more than ten yards from each other; these are crossed by feeders running from the con ductor to the lowest side of the field, thus forming a kind of checkwork. The main
drain is made as before, and the feeders, which taper towards their lower extremity, serve for small drains. This plan is more effective than the former, when the supply of water is limited; and as it can be applied to a hillside as well as to a level field, its appli cation is rapidly extending.
3. Subterraneous Irrigation ison]y applicable to perfectly level fields, and consists, first, of ditches being formed all round the sides. At right angles to these, drains or conduits are drawn across the field in parallel lines. When the laud is to be irrigated, water is let into the ditches, and thence to the cross-drains, till it rises to the level of the surface; and when the ground is to be laid dry, the side-ditches are emptied by sluices. The bottom of the ditches is below the level of that of the cross-drains, so that they serve both as conductor and main-drain.
The first two methods of irrigation are only applied to pasture-lands, and the third to fens and drained morasses, which are apt to become parched in summer; the last method would be very valuable for land under green crop in cases of drought.
The management of water-meadows requires great skill and care, but we can only here mention the chief points to be attended to, which are these: the water, if limited in quantity, must be confined to a part which it can effectually irrigate; too much water or too rapid a flow tends to wash away the soil; the meadow may he kept under water for a fortnight at a time, in Nov., but the time should be diminished till April or May, when regular watering should cease; after the grass is cut down, the water may be let on for a few days; and it is necessary that between the times of watering the land should be laid perfectly dry. Special precautions are necessary iu winter, to guard against any bad effects resulting from frost, etc.