PLOW, PLOWING. The first in order and importance of agricultural operations is the breaking up of the soil, and this is accomplished, in all countries where agriculture is in an advanced state, by inverting the upper stratum of earth upon which the plants grow. Such a mode also buries and destroys all weeds, leaving the surface clean and unencumbered. The inversion of the upper stratum is effected by turning over successive sods or slices, of the length of the field, and of varying thickness and depth, according to the nature of the succeeding crop, and the nature of the soil; a-nd the implement employed for this purpose is the plow. The general form of the plow is known to every one, and to the unobservant eye it appears to be a very simple and even primitive tool; never theless, much mechanical skill and ingenuity have been expended in perfectly adapting it to its work. It is a combination of instruments (fig. 1) fastened to a beam. GBL; the coulter, K, is an iron knife-blade for cutting the sod vertically; the share, CFD, which is merely a socket fitted on and not fastened to the body of the plow, has a sharp point, C, and a projecting horizontal edge, CO, on its right-hand side. Its part of the work being to separate the under-surface of the sod from the .subsoil; by means of the mold-board, the slice, now wholly separated from the firm ground, is raised up and turned over by the forward motion of the plow; and the stilts, or handles, one of which, BL,_ is a continua tion of the beam, the other, M, being fastened partly to the former by rods, and gartly to the lower portion of the frame work, are for the purpose of guiding the implement.. The front part of
the beam is formed with an upward curve; at its extremity is placed the•bridk, N, to which the horses are attached by means of swing-trees and chains or traces, and the object of which is to enable the workman to elevate or depress the line of draught, or move it to the right hand or the left, as may be found necessary. The left sides of the coulter, share, and framework, ADEB, should evidently be in the same ver tical plane. The form of the mold-board is of the utmost importance, and has chiefly attracted the attention of agricultural machinists since the time when improvements on the plow were first projected. Its office being to raise and turn the sod, it is necessary that the surface should slope upward and outward from the front, so as to apply a pres sure in both directions, and, accordingly, the surface is so shaped that from the point of time share, where it is horizontal, it gradually curves upward, till. at the extremity, P, it inclines over away from the body of time plow, The gradual change produced on the position of the furrow-slice is seen in tip. 2, where ABCD,, on the left-hand side, represents the slice untouched by the plow, AD being the line of section by the coulter; DC, by the share;• BC, the open side from which the previous furrow (E) to the right-hand side has been separated; and the four successive rectangles,