The Harrow I is drawn by the Beams, to which it is fastened to their Insides at d and e, having each a small Iron Pin, passing thro’ each End of the Legs of the Harrow, and thro’ the Beams; each having a Nut on the Outsides of the Beams, and being square in the Beams, that they may not turn therein to loosen their Nuts; but are round near their Heads, that the Harrow may easily move thereon.
The round Ends of the Legs of the Harrow are put thro’ its Head I, at the round Holes f and g; and pinned in behind it, to the end that either Tine of the Harrow may descend at the same time that the other rises, where the Ground is uneven.
The Two wooden Tines K and L are pinned in above the Head, and have each of them a Shoulder underneath. They stand sloping; so that if they take hold of any Clods, they do not drive them before them, but rise over them. They are of a convenient Length, to give room for the Harrow to sink and rise, without raising up the Shares; and to give them the more room to move: The Legs of the Harrow are crook’d downwards in the Middle.
The Distance of these Tines from each other is Twenty-two Inches; so that each Tine going Three Inches and an half on the Outside of each Chanel that is next it, fills it up with Earth upon the Seed, from the Outsides of it; which causes the Rows to come up something nearer the inner Sides of the Chanels, than to the outer Sides, from whence the Earth is brought into them by the Tines; and the Two outer Rows by this means come up at Fourteen Inches asunder, tho’ the Chanels were Fifteen Inches asunder.
This way of covering adds more Mould to the Top of a Ridge; whereas, if the Chanels were covered by Tines going within or between them, the Mould would be thrown down from the Top of the Ridge: And these Tines stand with their Edges and Points inclining outwards, by which means they bring in the more Earth to the Chanels.
If we find, that the Harrow is too light, we tie a Stone upon it, to make it heavier; and sometimes we fix a small Box of Board on the Middle of it, to hold Clods of Earth for that Purpose.
The fore Funnel C has its upper Edges Two Inches high above the Surface of the Plank. It is Five Inches Square at Top; its Four opposite Sides being Planes equally inclin’d to each other downwards, until they end at the Hole in the Bottom of the Funnel, which Hole is continued quite thro’ the Plank into the Trunk. The Shape of this Hole is shewn in [Fig. 9.] where the Four Lines a b, b c, c d, and d a, each Line being Three quarters of an Inch, make a true Square, and are the upper Edges of the Hole. The Three prick’d Lines e f, f g, and g h, being each of them longer than the former, tho’ as little as possible, make the Three lower Edges of the Hole; which being thus wider below than above, and having all its Sides true Planes and smooth, it is impossible for the Seed to arch therein. The fore Side of this Hole is perpendicular to the upper and lower Surfaces of the Plank, and, together with the Back of the Sheat, makes one Plane Surface.
When we drill a large Species of Seed, as Peas or Oats, we can make this Hole a full Inch square at Top, and of the same Shape wider at Bottom; which tho’ it be wider than the Trunk, except at its Top, the Seed will not arch there, because there is room behind, the Plates being broader than the Sides of the Hole; for there can be no Arching in the Trunk, unless the Seed were confin’d behind as well as on each Side.
The Holes of our Funnels ought to be of the same Shape with this described; tho’, as I am inform’d, the Pretenders to the making of this Plough make the Holes of their Funnels the Reverse of this; which being wrong-way upwards, the Seed is apt to arch in them, except the Holes are very large.