These Pastboards will be very useful to the Whitesmith, for directing him to find the Places where the Holes for the Axis of the Tongue, and those for screwing the Two Halves of the Mortise together, are to be made. I advise against boring the great Hole with a Tool (a Bit) with more than Four Edges; for it would be apt to tear the Brass.
The great Hole of the Turnep-drill is bored with Tools like those wherewith a Gun is bored. But the Wheat-drill is bored with a Screw-stock, whose Edges are made sharp for that Purpose, and may be set wider or narrower at Pleasure: It is put into the Hole along with an half-round Piece of Wood, the lower End of the Stock being set fast in a Vice: The whole Seed-box (for it must always be screwed together before it is bored), being put on the End of the Stock (made taper a little way for entering), is turned round it by a long wooden Spanner, which hath a Notch in the middle of it, to receive the whole Seed-box, in order to bore it by turning it round upon the Stock.
The Brass ought to be of the best Sort, which will be easy to file, and yet not mix with baser Metal.
The Seed-boxes may be cast whole by these Moulds; but I prefer those that are screwed together, for several Reasons, which I have not time now to write.
There is a Turnep Seed-box come to my Hands that was made by Pretenders; I wish it is the only one made in the same manner; for it is useless; the Notches in the Spindle are much shorter than the Breadth of the Mortise; at each End of the Notches is a deep Chanel (as deep as the Bottom of the Notches) quite round the Spindle, instead of a Mark, which should be but just visible for cutting the Notches; and instead of a tender Steel Spring, there is a strong Piece of Iron without Elasticity. By means of this Iron, the Machine grinds the Seed, instead of drilling it.
What I shall here add concerning the Wheat-drill, is some Alterations in [Fig. 21. of Plate 4.] viz. The fore Share and Sheat must be left out for drilling Wheat, up more middle Rows being used. And the Two Beams B B in the Plough, [Fig. 1.] must be set to make Chanels Ten Inches asunder. And the double Hopper, [Fig. 15.] must be set nearer together, so as the Seed may fall into the middle of the Funnels of the Beams.
Tho’ there is no Necessity of Marking-wheels for guiding the Drill-horse upon Ridges; yet they are very useful for holding the Drill steady, and to prevent its tottering, which without the Marking-wheels, and the fore Hopper, it is apt to do, when the Shares stand so near together as Ten Inches; and on a narrow Ridge one of the hinder Wheels might run off to the Furrow, and draw the Shares after it, if the Drill were not kept steady by the Marking-wheels, and by their Hopper, which takes hold of the single Standard by [Fig. 22.] as is seen in [Fig. 21. in Plate 4.] But there should not be so much room in it on each Side of the Standard, left the Plough by that means should have too much room to totter, now the Shares are so near together.
The Marking-wheels must be set at the Distance of the Breadth of Two Ridges, which, as we now make them, is about Nine Feet and an half from Wheel to Wheel.
The Brass Box may be taken out of the fore Hopper: And tho’ that Hopper be of no Use to the double Row, except as is abovesaid; yet if there should be Occasion to press the Marking-wheels deeper into the Ground for keeping the Plough the more steady in its Course, it may be usefully filled with Earth, or other Matter, sufficient for that Purpose. And besides, it may serve to plant Three Rows of St. Foin, when the fore Share and Sheat are put in, and the Beams and hinder Hopper set a Foot or Eighteen Inches wider, and the Marking-wheels at their due Distance, as is directed in the Essay. Thus the same Drill may plant Wheat and St. Foin.
A Drill for the double Rows might be made with a single hinder Hopper, instead of the double one. And there is a Contrivance to supply the Use of the fore Hopper for keeping the Plough steady, and more easy to make than that Hopper; but this cannot be described by Words without Cuts.