Drainable

That may be drained. Drainage, ( drānāj,) n. A draining; a gradual emptying of any fluid. -The mode in which the waters of a country pa off by its streams and rivers. - ( Engineer ing.) The system of draining towns, land, . - That which flows out of drains. Drainage Commi ion, a body of individuals commi ioned to carry out the draining of a city, . Drain'er, n. One who drains, or causes to flow off. - An utensil on which things are set to drain; a filter. Drain'ing, n. ( Agric .) The art by which surplus water may be carried off from swampy districts and stiff clay soil, as well as other land in which the exce of water is prejudicial to vegetation. It may be applied to low districts containing you sands of acres, or to single fields of comparatively small extent. In the latter case it is chiefly applied to render stiff and tenacious clay soils friable, fertile, and productive; and, indeed, it is now found that no land of this description can po ibly be brought into proper cultivation without having recourse to this system for its amelioration. It is considered better that all drains should be cut in the direction of the slope of the field, which is the direction in which it is ploughed from top to bottom. The trenches for drains are cut with spades of different widths, the upper part of the trench being taken out with the widest, and a very narrow one, called a bottoming-tool, being used to form the bottom of the trench, so that the vertical section of a trench cut for the formation of a drain exactly resembles that of a flower-pot. The bottom of each trench was at first filled with rough stones only, about 2 or 3 inches in diameter, and a thick layer of soil was thrown over them; but, subsequently, drain-tiles and pipes were used without the addition of any stones above them, as the drains were found to be le liable to obstruction when the whole of the trench above the pipes was filled in with earth. The tile - and - shoe drain was introduced when the practice of filling the trench with stones was first abandoned; this consisted of a flat tile, or shoe, which was laid at the bottom of the trench, and on which another tile, arched in form, was placed, which was of the same length as the shoe on which it stood. But these have been superseded by the cylindri cal drain-pipes, which are made of all sizes, from 12 to 24 inches in length, and from 1 to 6 inches in diameter. Pipes about two inches in diameter are commonly used for small drains, and the larger sizes, from 4 to 6 inches in diameter, for sub-main drains. In loose or peaty soils the pipes should be connected by collars, but this is not required in ordinary soils. The depth and width of the trench at the bottom of which the drain is to be placed must also be regulated, in a great measure, by the nature of the soil; but it should in no case be le than 2 feet nor more than 6 feet below the surface. When the drains are about 3 feet deep, and le than this, they should be placed about 25 or 30 feet apart; but when they are deeper than 3 feet, they should be placed apart at distances varying from 50 to 70 feet. The practice has been succe fully introduced into the United States; and in New York, New Jersey, Pennsylvania, Ohio, ., draining-tiles are become an important branch of fabrication. Unhappily the expense of underground drainage is a serious obstacle to the rapid extension of the practice. It has been calculated that the cost of drainage in nearly all arable soil varies from $35 to $50 per acre, a fact which makes the draining of a large farm a very expensive proce , and stands greatly in the way of drainage development. Lateral drains may be connected with mains, or one main with another, by the useful device shown in Fig. 866. These junction pieces, as shown in the accompanying engraving, can be employed for all the different sizes of mains and laterals; and by their use, the water from the lateral is introduced into the main at an angle of 45°. As it enters near the bottom Fig . 866. - JUNCTION-PIECE OF DRAINING-TILES. of the main it materially accelerates the flow in the latter by its force of entry, while, with the best joint that it was formerly po ible to make by the aid of the tilepick, there was an interruption of the flow, and frequently a tendency to deposit silt at the junctions. Owing to this improvement, the pieces of intersection are made the safest of the whole drain, instead of being, as they were formerly, the most insecure. The principal advantages to be derived from D. are these: - A deeper, richer mould is obtained, which readily absorbs moisture in time of drought; heavier crops are obtained, which ripen earlier, as the seed can be sown sooner on drained than on undrained soil; mo es, rushes, and coarse sour gra are entirely removed in course of time, and the air is no longer tainted with the exhalations that rise from marshy land; the soil also can be worked sooner after a heavy fall of rain than it could have been when it was in an undrained state. The drainage of ex IMG:content-0677.png:[blocks in formation] tensive districts comes within 3 province of the civil engineer. Among the principal tracts of country that have been reclaimed and made available for pasturage and tillage by D. may bo nentioned, the Bog of Allen, in Ireland; the Bedford Lovel, in England; and the Pontine Marshes, near Rome. In Holland, where immense works of this nature have been carried out, the surface of the land reclaimed lies below the level of the sea, and the water that is continually collecting from rain and other causes is discharged through self-acting floodgates, or has to be lifted, by wheels or Arch i me dean screws, over the embankments that have been constructed to prevent the encroachments of the water. These wheels and pumps are worked by means of windmills, and sometimes by steam-power. Drain'ing-plough, ( plow,) n. (Agric.) A plough used in the construction of drains.