Draw many Lines from the Middle of the foremost Hole of the Plank to the hinder Edge of it, at (suppose) a quarter of an Inch from one another there; and then bore a Hole in that Part of each Line that is least apt to break into the next Hole to it.
Every System of Holes in the Plank will have like Benefit of being increased in their Number by the Convenience of this Mortise; without which it is impossible to have so great Variety of turning the Point of the Share to make the Share go parallel to the Horse-path.
The Board described in [p. 403.] we now use very seldom in Hoeing of Wheat.
Explanation of [Plate VII.]
[Fig. 1.] shews the Plank and the Harrow of the latest and best Drill-plough, most simple, and accommodated to the present Practice of planting double Rows.
A is the Plank, with all its Mortises and Holes; b is the Mortise into which the Tenon of the fore Sheat of the Drill-plough, for planting treble Rows, was fastened; d is the square Hole for receiving the Seed from a Hole of the same Shape and Size in the Bottom of the Funnel.
When the Sheat is taken out of the Mortise b, and another Sheat is made exactly the same with that, place them in the Mortises a a, and make the Two square Holes c c behind them, for their Funnels to stand on. Make the Mortise e, which is to hold the single Standard that is to hold up the fore Hopper in the treble Drill, and in this to guide the Wheels also, instead of Wreaths, that in the treble Drill are put on the Spindle bearing against the Insides of the double Standards; for in this the Shares being but Ten Inches asunder, and at such a Distance from each of the Wheels, that neither of them doth by rising lift up a Share perceptibly; but if the Shares were wide asunder, or there were more of them reaching nearer to the Ends of the Plank, a Wheel might rise up, and lift a Share out of the Ground, if guided by the single Standard and Hopper, as in this. The single Standard is shewn in [Plate 4. Fig. 10.] but this has no Fork at its Bottom, as that has. This has only a single Tenon, and is shouldered before, behind, and on each Side, to hold it the more firm and steady, when tightly pinned down by Two Pins underneath the Plank. The Dimensions of this Standard are the same with those of the other; but the Shoulders must not increase the Thickness of the Standard any higher than the Tops of the Funnels.
The Four other square Holes, viz. f with another behind it, and g with one before it, are for the double Standards, which are to be well shouldered, or braced on the Side of each that is next to the End of the Plank, and on the Outside. There is no need of Shoulder or Brace on the Sides where the Spindle is placed, or on the Side next to the Middle of the Plank.
The Four round Holes h i k l are those thro’ which the Four Pins pass that hold on the Limbers, and the Piece A, in [Fig. 2.] and the other of the same Sort in [Fig. 4.]