ABCD to the right, illustrate the suc cessive changes of position of the furrow as the mold-board is pushed forward under and on its left side, till it is finally left, as represented in ABCD, on the right hand; E, F, G are furrows which have previously been laid in their proper position. The advantages of laying the furrows in the position shown are these: in the first place, the weedy side of each furrow being closely applied to the previous furrow, and kept pressed against it by its own weight and time pressure of the mold-board, the weeds are completely buried; secondly, the ridged surface thus presented affords the means of covering the seed by harrowing; and lastly, the openings below increase the amount of surface accessible to air, and drain off superfluous water. The modern plow is wholly formed of iron ; the share and the framework of malleable, and the mold-board of cast iron, or sometimes of steel; while the coulter is frequently, welded with steel on the right-hand side, the better to resist attrition. In most of the English (as distinguished from the Scotch) plows, wheels are attached at or near the front end of the beam, a contrivance which renders the implement more steady in its motion, more easily managed; and callable of doing better work in the hands (.1 inferior workman; but it is generally believed, in Scotland at least, that the plow with out wheels, or swing-plow, as it is technically termed, is greatly more efficient in the Lands of a thoroughly-skilled plowman. The usual dimensions of the furrow-slice in lea or hay-stubble are 8 or If in. in breadth by 6 in depth; and in laud for green crop, 10 in. in breadth, and 7 or 8 in depth. Shallower plowing is not utifrequently adopted, especially on thin soils, and in various parts of England. .Nor is it uncommon to plow stubble-land 10 in. or more in depth.
Other kinds of plows are used for special purposes, such as trench-plows, which are made on the same principle as the common plow, but larger and stronger, so as to bring up a portion of the subsoil to the surface; subsoil plows which have no and merely stir and break up the subsoil, thus facilitating drainage; double mold board plows, which are merely common plows with a moldboard on each side. and are employed for drilling turnip or potato land, for water-furrowing, and for earthing up potatoes, etc. Of each of these plows there are many varieties, each maker having
generally some peculiar views regarding the form and proportion of some parts of the instrument. For those who wish to study minutely the best form of plow, it w will be necessary to consult works on agriculture and agricultural implements. Thew is. how ever, one very peculiar form of plow sometimes used in various parts of England. which deserves more particular notice; this is the turn-wrest plow. Its chief peculiarity is, that instead of one, it has two moldboards, one on each side, and these are alter nately brought into operation, so that the furrow is always turned over in the smne direction. The moldboards are firmly fastened together in front, and kept at a con stant distance from each other behind by means of struts, while the handles are movable with reference to them; the mold board which is intended to be used being push( d away from, and the other (which for the time does the same work as the vertical surface ADEB in Fig. 1) brought nearer to the line of the beam; of course, when the next furrow is plowed, the mold-boards exchange adjustments. This form of plow is useful in plowing along a hillside, as by it all the furrows can be turned over towards the hill, thus preventing the natural tendency of the soil to work itself down*ards, leaving the upper portions bare. Some years ago the doable-furrow plow was intrcduce0. It con sists of an iron frame, similar in sonic respects to that of a grubber or cultivator, with two breast-plates, mold-boards, and shares; the one set a little back from the other, and so far distant as it is desired should be the width of the furrow. Two or three wheels bear the implements—one in front miming in the bed of the last excavated furrow, and the other one or two behind. There is a directing-rod, but no stilts. The double-fm row plow was at first singularly popular, and after a few years was found on almost every farm. It was, however, soon found that, generally speaking, the weight was too much for the draught of a pair of horses, and that, even on light land. three horses were required. In fact, the depth of tillage is in practice gradually increasing; so that, unless for a grain crop after either turnips or potatoes, these plows have been nearly laid aside.