DRAINING. The art of freeing the surface of the soil from superfluous wa ter, considered with reference to culti vated vegetables, and the health of man and animals. Water may become super fluous by being collected in the natural hollows on the surface, and thus form ing bogs ; by retained in the sur face stratum, in consequence of a retell five subsoil • or by oozing through a moist subsoil to the surface stratum, in consequence of supplies from subter raneous sources. Water collected in bogs, or marshy places, remains there, because it has no natural outlet, neither by an opening or hollow along the natural sur face, nor by the porosity of the subsoil, in consequence of which the water might sink into it and disappear. The obvious mode of draining in the first case is by a trench or drain, so deep as to draw the water from the lowest parts of the hollow, bog, or marsh. Where water is retained in the surface soil in conse quence of a retentive subsoil, as in the case of clays and many loams, the most effective mode is to cut a number of small drains parallel to and at short distances from one another ; and by the tops of these drains reaching within an inch or two of the bottom of the surface soil, which in cultivation is turned over by the plough, they absorb the superfluous water that passes through this soil and carry it off. Or, should the land be in pasture, the tops of the drain should be brought within an inch or two of the grassy surface, so as to intercept the water, both oozing laterally from the sur face soil, and vertically from among the leaves of the grass. It may be observed also that pasture lands on this descrip tion of retentive soil may be more rea dily drained when laid into ridges, and an underground drain formed under each furrow or surface drain. This, however, is not essential ; and though furrows or surface drains would be no deformity in field culture, yet in lawns and parks the appearance of furrows would destroy the continuity and evenness of surface, which in lawns is one chief source of beauty. To drain the surface soil, where it is supplied by water from the subsoil, re quires some knowledge of the strata of which the subsoil is composed. In gene ral the strata composing the subsoil lie over one another in a direction more or less approaching to horizontal ; and when the natural inclination of the surface is every where to this strata be the water, if it oozes out of the subsoil at all, will generally do so equally throughout the subsoil ; and in such cases numerous drains at no great dis tance are required to carry it off, pre cisely as in the case of draining soils with retentive subsoils. But when the line of surface does not correspond with the line of substrata, but intersects this line, then water will generally be found oozing out at the line of intersection, technically called the cropping out of the strata. The quantity of water which will
issue from these sections or croppings out of broken strata will dcptnd on a great variety of circumstances, into which it is unnecessary here to enter ; be cause in all cases the mode of draining is the same, viz., that of forming a drain parallel to the line of fracture of the strata. This drain in some cases is not required to extend the whole length of the line of the fracture ; because if the strata have a double inclination, so as it were to conduct the water to one angle orpoint, a drain at that angle or point will carry off the whole of the superflu ous water contained in the strata. The subsoil in some cases is composed of strata in a nearly vertical position, and in others of strata alternately depressed and elevated, so that a section through them would form a serpentine line ; and sometimes the subsoil is composed of strata the layers of which have been broken up and jumbled together. All these, and other cases, are to be drained in one or more of the above described modes ; that accumulated water, whe ther in the soil or above it, is to be let off by cuts or drains made at the lowest points of accumulation ; and surface soil saturated with water, whether from greater atmospherical supplies than can be carried off by evaporation or can sink into the subsoil, or whether it arise from sources in the subsoil, is to be carried off by numerous drains close to one another, and the tops of which are the cultivated soil, or the permanent cloth ing of grass or other herbage.
Draining is not required in this coun try as much as in England ; yet in very ninny instances, as in heavy clay soils and on low swamp lands, it should be the first step in the cultivation of the land. When the soil is porous, light, and sandy, drains are not required ; or if so, need only be placed far apart and at great depth (below 5 feet) : on clay lands they require to be closer, and about the depth of 80 or 86 inches. Draining tools and tiles are now coming into much use ; and when it is considered that it raises the produce of the land to one third more, few intelligent farmers who cultivate well will neglect it. Pipe drains are better for general use than arch drains with flat soles, as the water is de livered quicker in its channel, and the latter is kept clean, not choking up : the latter, however, hold better in clay soils.
The top of every drain should be suf ficiently far below the surface that the plough in passing over will not touch it. DRILL. In mechanics, a small instru ment of steel for perforating metals or hard substances. Its action is produced by communicating to it a very rapid ro tation by means of a drill-bow.