The Distance of Two Inches and an half, by which each of the Three added Coulters stand more to the right Hand than that immediately behind it, must be reckoned from the Middle of one Hole to the Middle of the other. The Fore-part of every Hole must incline a little towards the Left; so that the Backs of the Coulters may not bear against the left Side of the Incisions made by the Edges. Each Hole, being a Mortise, is one Inch and a quarter wide, with its Two opposite Sides parallel from Top to Bottom; each of these Mortises, or Holes, are long at Top Three Inches and an half, and at Bottom Three Inches; the Back-part, or Hinder-end, of each Coulter-hole is not perpendicular, but oblique, and determines the Obliquity of the Standing of the Coulter, which is wedged tight up to it by the Poll-wedge _i_, _Fig._ 1. as all Coulters are. _Fig._ 17. Is a Coulter; _a b_ is its Length, being Two Feet Eight Inches, before it is worn; _e d_ is its Edge, Sixteen Inches long; _d c_ is the Length of its Handle, Sixteen Inches; this is made thus long, at first, to stand above the Plough, that it may be driven down lower, according as the Point wears shorter; this Handle is One Inch and Seven Eighths broad, and Seven Eighths of an Inch thick, equally thro’ its whole Length: Its Breadth and Thickness might be described by a rectangled Parallelogram. In all Ploughs this first Coulter is, or ought to be, placed in the Beam in manner following; _viz._ its Back to bear against the Back of the Coulter-hole, its right Side above to bear against the upper Edge of the Coulter-hole, and its left Side to bear against the lower Edge of the Coulter-hole; so that always Three Wedges at least will be necessary to hold the Coulter; the Poll-wedge before it, as at _i_, in _Fig._ 1. another Wedge on the left Side of it above, and a Third on the right Side underneath: The Coulter-hole must be so made, that the Coulter standing thus across the Hole, its Point may incline so much towards the Left, as to be about Two Inches and an half farther to the Left[260] than the Point of the Share, if it were driven down as low as it; but it never ought to be so low in any Plough: As to its bearing forwards, the Point of the Coulter should never be before the Middle of the Point of the Share: What Angle the Coulter would make with the Bottom of the Share, may be seen by the Posture it stands in, in _Fig._ 1. If it should be set much more obliquely, it would have a greater Force to raise up the Poll-wedge, and get loose. [260] I find that sometimes it is necessary in some of these Ploughs for the Point of this Coulter to stand yet farther on the Left of the Share’s Point.