[Fig. 5.] Is the Share; a is the End of the Point; b is the Tail of the Share, long from a to b Three Feet Nine Inches; c the Fin; d the Socket, into which the Bottom of the Sheat enters; e a thin Plate of Iron riveted to the Tail of the Share: By this Plate, the Tail of the Share is held to the hinder Sheat, as at d in [Fig. 1.] by a small Iron Pin with a Screw at its End, and a Nut screw’d on it on the inner or right Side of that Sheat. From a to f is the Point, long about Three Inches and an half, flat underneath, and round at Top: It should be of hard Steel underneath. From f to c is the Edge of the Fin, which should be well steeled; the Length of it is uncertain, but it should never make a less Angle at f than it appears to make in this Fig. The Socket is a Mortise of about a Foot long, at the upper Part, Two Inches deep: The Fore-end of this Mortise must not be perpendicular, but oblique, conformable to the Fore-part of the Sheat which enters it; the upper Edge of which Fore-part must always bear against the Sheat at e in [Fig. 4.] but if this End of the Socket should not be quite so oblique as the Sheat, it may be help’d, by taking off a little of the Wood at the Point c.
[Fig. 6.] Shews the Share, with its right Side upwards, in the same Posture as when it plows; whose Side a b should be perfectly strait, but its under Side at c, which is its Neck, should be a little hollow from the Ground, but never more than half an Inch in any Plough, and a Quarter of an Inch in a Four-coulter Plough; so that the Share, when it is first made, standing upon its Bottom, bears upon the level Surface only in Three Places; viz. at the very Point a, at the Tail b, and at the Corner of the Fin d.
[Fig. 7.] Is the Share, turn’d Bottom upwards; and shews the Concavity of the Fin at a; which must be greatest in a stony rubbly Soil.
[Fig. 8.] Shews the Share, the right Side upwards, but leaning towards the Left.
In placing of the Share rightly upon the Sheat, consists the well going of a Plough, and is the most difficult Part of a Plough-wright’s Trade, and is very difficult to be shewn. Supposing the Axis of the strait Beam, and the left Side of the Share, to be both horizontal, they must never be parallel to each other; for if they were, the Tail of the Share, bearing against the Side of the Trench, as much as the Point, would cause the Point to incline to the right Hand, and go out of the Ground into the Furrow. If the Point of the Share should be set, so that its Side should make an Angle on the right Side of the Axis of the Beam, this Inconvenience would be much greater; and if its Point should incline much to the Left, and make too large an Angle on that Side with the Axis of the Beam, the Plough would run quite to the left Hand; and if the Holder, to prevent its running out of the Ground, turns the upper Part of his Plough towards the left Hand, the Fin of the Share will rise up, and cut the Furrow diagonally[259], leaving it half unplow’d; beside, the Plough will rise up at the Tail, and go all upon the Point of the Share: To avoid these Inconveniences, the strait Side of the Share must make an Angle on the left Side of the Beam, but so very acute, that the Tail of the Share may only press less against the Side of the Trench than the Point does. This Angle is shewn by the prick’d Lines at the Bottom of [Fig. 1.] where the prick’d Line e f is supposed to be the Axis of the Beam let down to the Surface, and the prick’d Line g f parallel to the left Side of the Share; but this Angle will vary as those Two prick’d Lines are produc’d forwards to the Fore-end of a long and a short Beam, keeping the same Subtense: For Plough-wrights always take this Subtense at the Fore-end of a Beam, whether it be a long Beam or short one; and it is the Subtense e g, that determines the Inclination the Point of the Share must have toward the left Hand. Plough-wrights differ much in this Matter; but, by what I can learn by those that make the Ploughs I see perform the best, this Subtense at the Fore-end of an Eight-feet Beam should never be more than one Inch and an half; and by full Experience I find, that whether the Beam be long or short, the Subtense must be the same; for when my Plough-wrights take this Subtense at Eight Feet from the Tail, when they make my Four-coulter Plough, whose Beam is Ten Feet Four Inches long, the Point of the Share will incline too much to the Left, and it will not go well until this Fault be mended, by taking the same Subtense quite at the End of the Beam; which makes the mentioned Angle more acute.
[259]This is the greatest Misfortune incident to a common Two-wheeled Plough, and happens generally by the Fault of the Maker, though sometimes by the Plowman’s setting it so, that the Point of the Share turns too much to the Left. I have seen Land plowed in this manner, where not half of it has been moved, nor better tilled than by Raftering, not only cut diagonally, but also half the Surface hath remained whole, where when the Earth that was thrown on it was removed, the Weeds appeared unhurt on the unplowed Surface. In this Case, they for a Remedy let the Plough to go deeper; and then, if it go deep enough for the Fin to cut off the Furrow at a just Depth, the Point will go below the Staple, which may ruin the Soil, unless it be very deep.
When our English Ploughs go in this manner, they make much worse Work than the Eastern Ploughs, that have no Coulter; for these, contrary to ours, though they always cut their Furrow diagonally, cut it thin on that Side from which it is turned, as our bad Ploughs leave it thin on that Side towards which it is turned. The Earth the Easterns leave by their Diagonal in one Furrow, is taken off by the next; but ours leaving Part of their Furrow behind them, on the Side next to the plowed Part of the Field, come at it no more; but the other can plow cleaner, their Diagonal being contrary to ours, which leaves the Trench deepest on the Side next to the unplowed Part of the Field; but unless the Fin of the Four-coultered Plough go parallel to the Surface of the Earth, it will not plough at all; or will leave Two or Three of its Four Furrows untouched.