This drain must be deep, and therefore, must be wide and sloping, so that it may be kept open; and it should be curved round, following the line of the upland to the outlet. Often it has been found, in England, that a single drain, six or eight feet deep, has completely drained a tract of twenty or thirty acres, by cutting off all the sources of the supply of water, except that from the clouds. This kind of land is very porous and permeable, and readily parts with its water, and is easily drained; so that the frequent drains necessary on uplands, are often quite unnecessary. Many instances are given, of the effect of single deep drains through such tracts, in lowering the water in wells, or entirely drying them, at considerable distances from the field of operation. When the surface-water and shallow springs have thus been cut off, the drainer will soon be able to determine, whether he has effected a cure of his dropsical patient. Often it will be found, that deep seated springs burst up in the middle of these low tracts, furnishing good and pure water for use. These, being supplied by high and distant fountains, run under our deepest drains, and find vent through some fracture of the subsoil. They diffuse their ice-cold water through the soil, and prevent the growth of all valuable vegetation. To these, we must apply Elkington's system, and hit them _right in the eye_! by running a deep drain from some side or central drain, straight to them, and drawing off the water low enough beneath the surface to prevent injury. A small covered drain with two-inch pipes, will usually be sufficient to afford an outlet to any such spring.