PLOUGH

(Germ, pflug.) An implement drawn by horses and guided by a driver, by which the surface of the soil is cut into longitudinal slices, and succe ively raised up and turned over. The object of the operation is to expose a new surface to the action of the air, and to render it fit for receiving the seed, or for harrowing, or for other operations of agriculture. Ploughs are of two kinds: those without wheels, commonly called swing-ploughs; and those with one or more wheels, called wheel-ploughs. The e ential parts which compose both kinds of ploughs, £fre, the beam by which it is drawn; the stilts or handles by which the ploughman guides it, being two levers connected with the beam; the coulter fixed into the beam, by which the furrow-slice is cut; the share, also attached to the beam, by which the slice is raised up; and, finally, the mould-board, by which the slice is turned over. The most improved form of the swing-plough is that in general use in Scotland and the North of England, which is known as a modification of what is called Small's improved swing plough. The most improved wheel-plough is the same implement, with a wheel attached to the beam, for the purpose of keeping the share at a uniform distance beneath the surface. The subsoil plough, the invention of Mr. Smith, of Deanston, in Stir lings hire, is the swing-plough, of a somewhat stronger construction than that in common use, but without the coulter and the mou!d-board. The use of this implement is to follow the common plough, and loosen the subsoil at the bottom of the furrow without raising it to the surface. The most improved form of this implement contains a muzzle (the instrument by which it is drawn,) so contrived as that the horses may walk on the firm soil. The use of the subsoil-plough is one of the greatest modern improvements that has been introduced into the culture of arable land. Draining-ploughs are of different kinds. The mole-plough, instead of a share and mouldboard, has a small iron cylinder attached to the lower extremity of the coulter, and which, being drawn through gra land, leaves in its track a small opening, which has been compared to the underground track of a mole, and into which the water percolates from the surface through the narrow slit formed by the upper part of the coulter, and is thus carried off to an cpen drain. The other kinds of draining ploughs cut out the soil, raise it to the surface, and turn it over in the manner of the common plough, thus leaving a deep furrow, which is commonly farther deepened and modified by the spad'!, and afterwards partially filled with stones, draining tiles', or other materials through which water may find its way, and finally, covered with the surface soil. Draining-ploughs, though, in theory, promising a saving of manual labour, yet, in practice, are found inconvenient, from the number of horses required to work them. Their use is, therefore, generally confined to free, deep, loamy soils, with an even surface. [s. 960]