iron, which is nearly as wide as the drag, 7 inches in diameter; runs on its axis at d; has a strong shoulder; and, as it projects, resists the sudden jolts of rough roads.e, Is the chain to be fastened to the near shaft, in order to keep the drag properly under the wheel, which, from being violently jerked, might be apt to pass over the drag, and leave it behind: this is a necessary precaution, though seldom wanted, if the drag be well constructed.
In the shoulders marked 1, 2, are holes, by which the drag is suspended on hooks beneath the tail of the cart, when it is not employed.
This machine is, doubtless, susceptible of many improvements, especially in the size and construction of the wheel. By frequent use, the part to which the greatest pressure is applied, will necessarily wear away, and thus injure the drag: to prevent this accident, it ought to be shod, at first, with a plate of iron, or steel, fixed by means of two holes in its bottom; in which, when necessary, a similar piece may be inserted.
DRAGON's BLOOD, a foreign drug, more useful for staining than as a medicine.—See Marble.
DRAINING is the art or practice of making artificial channels, for carrying off superfluous moisture or water from wet or marshy lands.
This highly useful art did not generally engage the attention of agriculturists, till about the middle of last century. It was formerly practised by persons, called undertakers, who received one-third of the drained land as a recompense. The advantages to be derived from their labours being obvious, several public-spirited men of talent have lately, with considerable success, investigated the subject; and with great exertions, not only rendered the most boggy and unfruitful soils firm and stable, but in many instances, so mush improved their fertility, as to be productive of the finest grain.
Lands to be drained are usually divided into two classes: 1. Uplands, or those which are situated so high, that the water can descend from them, if properly collected and conducted; and, 2. Fens, marshes, or those lands which lie so low as to command no fall; have no descent; and some being even below the level of the sea.
I. With regard to uplands, it generally happens, that the waters from the springs beneath the soil are obstructed in their course to the neighbouring rivers. These springs originate from the atmospheric moisture; which, being condensed on the summits of hills into water, by the greater coldness of those parts, perforates the different strata of the incumbent soil, where it is of a porous nature; the water continues to descend, sometimes for many miles together, but generally from the nearest eminences into the adjoining valley, till its course is intercepted by a stratum of clay; where, being collected in considerable quantities, it is forced to work itself a passage through the porous strata of sand, gravel, or rock, that may be above the clay, following the course of these strata, till they approach the surface of the earth, or are interrupted by any obstacle, which causes the water to rise to the surface, and to form springs, bogs, marshes, &c.
At the foot of hills, therefore,
