Part 27

It is necessary also, that when you plow very shallow, the Fin of the Share be broad enough to cut off the Fourth Piece or Furrow; else that, lying fast, will be apt to raise up the Ground-wrist, and throw out the Plough: But when you plow deep, the Ground-wrist will break off this Fourth Furrow, altho’ the Fin be not broad enough to reach it.

Sometimes the First or left Furrow is apt to come through betwixt the First Coulter and the Sheat, and so falls on the left-hand Side of the Plough: This is no Injury; but yet it is prevented, by letting the Second Coulter stand a little higher than the Third; and then the Second Furrow, holding the First at its Bottom, will carry it over, together with itself, on the right Side by the Earth-board; but yet never set this, or any of the Three added Coulters, so high that they may not cut through the Turf. But as for the first Coulter, tho’ it should cut but an Inch or Two within the Ground, the Share will break off the first Furrow in raising it up.

Remember, as often as the Point of any Coulter is worn too short, that you drive down the Coulter with a large Hammer, carried for that Purpose; and when it is driven low enough, fasten the Wedges again, so as to keep the Coulters in their right Postures, that their Incisions may be all of them equidistant.

_Fig._ 18. Is a Nut, with Two of its opposite Corners turn’d up, by which it is driven round by a Hammer, and has so great a Force, that Three of them, with their Screws properly placed, hold the Piece, _Fig._ 16. as fast to the Plough-beam, as if they both were made of one Piece of Wood; but as often as the Wood shrinks in dry Weather, the Nuts must be screw’d farther on, both here and in all other Places where they are used: particularly, those which hold up the Retch; for if the Sheat should once get loose, there is no Cure but by a new one.

Betwixt this Nut and the Wood, there should be a thin Iron Bolster, about the Thickness of a Shilling, broader than the Nut, to prevent the Nut from eating into the Wood, especially when it is to be often screw’d, as on the Retch of these Ploughs, and most of all on the Hoe-plough; but sometimes we use a Piece of Shoe-leather instead of an Iron Bolster.

_Note_, There must be Iron Plates upon all the Coulter-holes both above and below, Three of which are seen on the Piece in _Fig._ 16. There is no need to say how they must be nailed on with many Nails made for the Purpose.

_Fig._ 19. Is the Iron Collar, fastened to the Beam by Two short Crooks A, B, which take hold of Two short Pins driven into the Plough just behind the Second Coulter-hole, one on one Side, and the other on the other Side of the Beam. The Crook A is seen on the left Side of the Beam near _c_, in _Fig._ 2. the Crook B doing the same on the other Side of the Beam, which is seen near _a_, in _Fig._ 3. C is the Crook (for its Shape called a C) which holds the Tow-chain to the Collar by the Link D, being Part of the said Chain taking hold of its Fore-claw; the other Claw taking hold of one of the Five Notches of the Collar: This Collar is partly seen at _d_, in _Fig._ 2. Both the Claws of the Crook (or C) turn upwards, so that they cannot take hold of any thing that may rise under the Plough: The Use of the Notches is to help the Direction of the Point of the Share, which has been described by the prick’d Lines under _Fig._ 1. As the Point of the Share wears, it inclines a little more towards the Right, and is remedied by moving the Crook into a Notch nearer to the Left, which will direct the Point a little more towards the Left: This is more easy to be done here than in the common Plough, whose Collar moves round the Beam: We can, by changing the Crook from one Notch to another, incline the Point of the Share towards the Right or Left at Pleasure. The Length of each Side of this Collar is a Foot long.

The Tow-chain is best seen in _Fig._ 3. where the Link Y is that which passes thro’ the Box, and is pinned in by the Stake, as has been shewn in _Fig._ 1. which Stake is commonly nailed to the Box, to prevent its rising up. When we would draw up the Plough a little nearer to the Crow-staves, we take hold of the Crook by a Second or Third Link. _Note_, That the shortening of the Chain does also a little incline the Point of the Share towards the Left.

_Fig._ 20. is the Iron-wilds. The Leg A is of one Piece with that which has the Notch, and that passes thro’ the Leg B by the Loop at _a_; both which Legs pass thro’ the Box, and are pinned in behind it, by the crooked Pins C, D. This Figure is seen with its Crooks on it, both in _Fig._ 1. and _Fig._ 2. _Note_, That the Holes in the Box, thro’ which these Legs pass, must not be made at right Angles with the Box, but must incline upwards, so that the Fore-part of the Wilds may be higher than the Hinder-part, or else the Upper-part of the Crow-staves would lean quite back when the Plough is drawn. If the Beasts that draw immediately next to the Plough be very high, their Traces must be the longer; else they and the Wilds making too small an Angle with the Tow-chain at the Box, when they draw hard, the Wheels will rise from the Ground, and be apt to overturn: This Angle I suppose should not be less than of 160 Degrees, and the Angle made by the Tow-chain or Traces that are drawn by the Cattle that go before them, will make an Angle with the Tow-chain at the Box yet much more obtuse. The Use of these Notches in the Wilds is, to give the Plough a broader or narrower Furrow: If the Links are moved to the Notches on the right Hand, it brings the Wheels towards the left Hand, which gives a greater Furrow; and when the Links are moved towards the left Hand, it gives a less Furrow, by bringing the Wheels towards the right Hand.

The Distance betwixt the Two Legs of the Wilds is Eight Inches and an half; the Length of the Legs is Nineteen Inches. They must be of convenient Strength. The Links being placed in Notches distant from one another, prevents one Wheel from advanceing before the other; which would happen, if the Links were both in One Notch, or in Two adjoining Notches, except they were middle Notches: These Links are each Six Inches and an half long.

E is the Ring, by which the Two Links, and the Two Crooks F and G, are held together, and on which they all move.

The Height of the Wheels in _Fig._ 2. The left-hand Wheel is Twenty Inches Diameter; the Diameter of the right Wheel is Two Feet Three Inches; the Distance the Wheels are set from each other at the Ground, is Two Feet Five Inches and an half; the Crow-staves are One Foot Eleven Inches high, from the Box to the Gallows; they both stand perpendicular to the Box, and the Distance between the Crow-staves is Ten Inches and an half. The Pillow is pinned up at its Ends by Two small Iron Pins, which are chained to it, that if they drop, they may not be lost. These appear in _Fig._ 1. and _Fig._ 2. The Height from the level Surface, up to the Hole in the Box, where the Tow-chain passes through it, is Thirteen Inches (being Two Inches below the Holes of the Wilds, on the Hinder-side of the Box); the Height at the other End, where the Crook of the Collar takes hold of the Pin in the Beam at _c_, in _Fig._ 2. is Twenty Inches high above the same level Surface, and shews how much the Chain descends forward, for drawing down the Plough, and by which Descent may be known what Angle the Chain would make with the Surface, if it were produced forwards in a strait Line; which is a thing material for the good going of a Plough; and so is the Angle the Tow-chain makes with the Beam: About the Middle of this Tow-chain, there should be a Swivel, whereby one End of the Chain may turn without the other.

When this Four coulter Plough is made, I would advise, that it be tried with only the first Coulter, before the other Three are put in; for if the Plough does not go well with One Coulter, it is not likely it should go well with Four; and I never yet have seen or heard of any that went well with One Coulter, that did not also go well with Four, being placed as is here directed.

The Proofs of a Plough’s performing well are these; _viz._ If it makes a Furrow of an equal Depth on the right Hand and on the left, and turns it off fairly: If, in its going, the Tail of the Share, and the Bottom of the Drock, bear against the Bottom of the Furrow; and if it goes easy in the Hands of the Holder, without pressing one Arm more than the other; then the Plough is certainly a good one.

The Ploughman who is accustom’d to a Two-wheel’d Plough, never suffers the Wheels to overturn, in turning out at the Land’s End, from one Furrow to another; for which Purpose, after he has lifted the Plough a little round, he has a Knack of holding up the Crow-staves with the End of the Beam, by pressing his Hand hard against the Handle, whilst the Plough lies down on one Side, until the Horses, the Wheels, and the Plough, come near to a Line in the Beginning of the Furrow; and then he lifts up his Plough, and goes on.

CHAP. XX.

_Of the Drill-Boxes._

The Drill is the Engine that plants our Corn and other Seeds in Rows: It makes the Chanels, sows the Seed into them, and covers them at the same time, with great Exactness and Expedition.

The principal Parts of the Drill are, the Seed-box, the Hopper, and the Plough, with its Harrow.

Of these the Seed-box is the Chief: It measures (or rather numbers) out the Seed which it receives from the Hopper: It is for this Purpose as an artificial Hand, which performs the Task of delivering out the Seed, more equally than can be done by a natural Hand.

It is described, together with some of its Appurtenances, in _Plates_ 2 and 3.

_The_ MORTISE.

As the Seed-box is the principal Part of a Drill, so is the Mortise the principal Part of the Seed-box.

The following Descriptions shew how this Mortise differs from a common Mortise.

Fig. 1. _Plate_ 2. shews both the upper and lower Edges of a Turnep-Seed-box, and the Manner how they are posited one over another, _a b c d_ is a rectangled Parallelogram, and shews the upper Edges (or Top) of the Mortise. _e f g h_, being a Figure of the same Denomination with the former, is the lower Edges (or Bottom) of the Mortise. The Line _e h_ is the Length of the lower Edge of the Hinder-end of the Mortise. _a d_ is the upper Edge of the Hinder-end of the Mortise, and posited just over the lower Edge of the same End. The Space between the Line _a b_, and the Line _e f_, shews half the Excess whereby the Bottom of the Mortise exceeds the Top in Breadth; as the Space on the opposite Side, betwixt the Line _c d_, and the Line _g h_, shews the other Half of that Excess, both which Halves, taken together, shew the whole Bevel (or Angle of Inclination) described in _Fig._ 2. That Part of the Line _a b_, from the Angle at _b_ to the Line _f g_, which intersects it, shews the Excess whereby the Top of the Mortise exceeds the Bottom in Length.

_Fig._ 2. Is the Mortise cut down by its Four Corners, and laid open. _a b c d_ is a Trapezium, with Two parallel Sides, and mark’d A, the right Side of the Mortise; its opposite Side _e f g h_, mark’d B, the left Side of the Mortise; the Areas of both being true Planes[261].

[261] Take care that these opposite Sides be sure to be true Planes, especially all that Part of their Areas, that is before the transverse Axes of their Ellipses herein after described; for should they be otherwise, the Bevel of the Mortise would be spoiled, and so would the Ellipses, and the acute Triangles, on the Sides of the Tongue; which how necessary they are to be true, is shewn in the proper Place. Workmen are very apt to fail in this when they file by Hand, and make these Sides of the Mortise convex instead of plane. Therefore this might be done with less Difficulty, and more Exactness, with a File placed in a Frame, whereby it might move upon a true Level without rising or sinking of either End.

_d i k h_ Shew the Fore-end of the Mortise, mark’d C. _a l m e_ shew the Hinder-end of the Mortise, mark’d D. _a d h e_ shew the Bottom of the Mortise already described in _Fig._ 1. If these opposite Sides and Ends were all raised up, until the Angle at _b_ join the Angle at _l_, and that at _m_ join _f_, and that at _g_ join _k_, and that _i_ join _c_, the Top of the Mortise would be formed, and the same with the Parallelogram _a b c d_, in _Fig._ 1. and then the intire Mortise of the Turnep Seed-box would appear in its true Form, standing upon its Bottom.

This differs from a common Mortise, in that it is impossible to fit it with a Tenon; because it is narrower above, and shorter below, as in _Fig._ 1.

The Areas, or imaginary Planes, of the Top and Bottom of the Mortise, are parallel to each other, but not equal.

Its Two opposite Sides are equal, but not parallel, by reason of their Inclination to each other upwards, which is the Bevel hereafter to be described.

The Two Ends are neither parallel nor equal, because the Hinder-end D is perpendicular to the Top and Bottom, and the Fore-end oblique, and therefore longer.

When Two opposite Sides, or Surfaces, are inclined to each other upwards, I call that Inclination a Bevel; but when they are inclined downwards, I call it a Bevel revers’d.

The Line _a e_, being the Bottom, or Base, of the Hinder-end D, by being longer than the Line _l m_, shews that the Mortise is bevel.

The Two prick’d Lines _m n_ and _l o_, with the Line _l m_, and Part of the Line _a e_, make a rectangled Parallelogram, which shews the exact Depth of the Mortise, and forms on each Side of it a rectangled Triangle, the one _m e n_, and the other _l o a_; which Triangles being similar and equal, and their acute Angles at _l_ and _m_ being each of Four Degrees, make the whole Bevel, or Inclination of the Sides of the Mortise, to be of Eight Degrees, their Hypothenuses being the same with the Sides of the Mortise.

This End D, being raised up to its Place, will be at right Angles with the Plane of the Top and of the Bottom of the Mortise; which, being both rectangled Parallelograms, prove that Bevel, or Angle of Inclination, to be the same from one End to the other of the Sides, which Sides are the Hypothenuses of those Two Triangles: But this could not be proved by the Triangles in the opposite End C; because the Bases being the same with the other, and having their Legs longer, the vertical Angles at _k_ and _i_ are more acute. The Legs are longer; because the End C, when in its Place, is not at right Angles with the Top and Bottom of the Mortise, as the End D is.

The next thing to be described in the Mortise, is the Bore, great Hole, or Perforation; which is best shewn in the Side of a Mortise of a Wheat-drill, being larger, as in _Fig._ 3. wherein _c e b d_ is the great Hole, and is a Section of an hollow Cylinder, that passes through the Mortise, with its Axis parallel to the Edges of the Ends of the Mortise: This Cylinder, being cut by the Side of the Mortise obliquely, and not parallel to its Base, is an Ellipse.

The prick’d curve Line is a Circle parallel to the Base of the Cylinder, and the curve Line _b d c e_ is the Ellipsis; and this Curve is more or less elliptical (or oval) in proportion to the Angle of Inclination, or Bevel, of the Sides of the Mortise.

Of this Ellipse the longest Diameter (or _Axis transversus_) _b c_ is at right Angles with the upper and lower Edges of the Sides of the Mortise.

Its shortest Diameter (or _Axis rectus_) _d e_, is the Diameter of the Cylinder, bisecting the _Axis transversus_ at right Angles in the Centre _a_; and is in this Figure one Inch and an half.

This Ellipse being concentric with the Circle, the Letter _a_ is the Centre of both.

The Semi-ellipsis _c e b_ is the Part of chief Use; and therefore the Edge must of Necessity be smooth, and without Flaws, as must the Surfaces of the Sides of the Mortise betwixt the Ellipse and the Fore-end.

The Tongue of the Seed-box (_Plate_ 3. _Fig._ 1.) differs from that in the Sound-board of an Organ (from which I took the Idea of it) in Shape, in Situation, and in the Manner of its being fix’d to the Mortise.

The Tongue, in the Organ, is on its Surface a long Square, or rectangled Parallelogram, a little broader and longer than the Mortise (or Grove) it shuts against; but this Tongue on its upper Surface, which is here turned downwards, being a Plane, is a Trapezium, of the same Shape with the Fore-end of the Mortise just now described, except that the Tongue has a less Bevel.

The Situation of that in the Organ is on the Outside of the Mortise, which it shuts by its Spring behind it, and opens immediately by the Finger of the Organist pressing down the Key to let in the compressed Air to its Pipes; but this Tongue is situate within the Mortise of the Seed-box, and placed almost, in a manner, diagonally; for, had it been placed like the other, the Seed getting betwixt it and the Edges of the Mortise, would not have given Way to its Shutting (as the Air does to the other), but have kept it always open; which would have render’d it useless for sowing of Seeds.

The Manner of fastening the Organ-tongue to its Mortise is by Parchment and Leather glu’d to its Surface, and also to the Sound-board, at its End which is opposite to that pressed open by the Key, and shut by the Spring; but this our Tongue is held within the Mortise, and moves on an Axis, which passes thro’ its upper and narrower End, which Axis is the Pin A (which must be exactly parallel to the Edge of the End of the Mortise), and also thro’ the Hole _f_ in _Fig._ 3. in _Plate_ 2. which is seen in its Place at A in _Fig._ 3. _Plate_ 3. and likewise through both Sides of the Mortise near their upper Edges, and as near the Fore-end of the Mortise as may be, without the Tongue’s rubbing against the said Fore-end.

The Breadth of the Tongue must be conformed to the Breadth and Bevel of the Mortise, and when it is on its Axis, it being raised tight up as far as the short prick’d Line _l m_ in _Fig._ 3. _Plate_ 2. being One-eighth Part of the great Hole, and being there, you see its upper Edges touch both Sides of the Mortise by their whole Length: Then it is rightly made: and by this touching both Sides of the Mortise tightly and closely, when raised up to that Degree, it appears, that the Two upper Edges of the Sides of the Tongue are inclined to each other in an Angle that is more acute, by about One-third, than is the Angle of Inclination of the Sides of the Mortise.

Hence, when the Tongue is let down to its Place, there will be on each Side of it an empty Space, betwixt it and the Mortise, of the Form of a very acute Triangle, whose vertical Angle is more or less acute, according as the Tongue approaches nearer to, or recedes farther from the Spindle.

This _Fig._ 1. _Plate_ 3. is the brass Tongue with its Back-side upwards. The Two outer Lines _a b_ and _c d_ are the Edges of the upper Surface (tho’ turned downwards in this Figure), which are inclined to each other, as afore-mentioned; but the Two inner Lines _e f_ and _g h_ are nearer to each other, whereby this under Surface is narrower than the upper: Both must be plain Surfaces, but the upper and its Two Edges very free from Flaws, and smooth, or polished.

The Reason why the under Surface is narrower than the upper, is to preserve the Bevel of the empty Triangle: For though the Bevel of the Sides of the Mortise would be sufficient for this, if both Sides of the Tongue were sure to keep equally distant from the Spindle; yet as the Tongue never is so tight on its Axis, but that sometimes one Corner of it may be nearer to the Spindle than the other, in this Case, that Side which is nearest to the Spindle would reverse that Bevel, so as to make the small empty Space that is betwixt the Mortise and the Tongue, wider above than underneath.

C C are the Two little Knobs that prevent the Spring from slipping to either Side, and are at the Distance from one another of the Breadth of the Spring.

_Fig._ 2. shews one Side, and the Thickness of the Tongue the other Side, being the same. _a b_ shews the polished Surface (being a true Plane), whereon the Seed runs down to the Spindle. _c d_ the Back-side, which lies turned uppermost in _Fig._ 1. _b e d_ shews one End of the hollow Cylinder of the Tongue, thro’ which its Axis passes.

The Length of the Tongue must be such, as will reach lower than just to touch the Bottom of the great Hole as a Tangent: for, if it be not longer than that, it might happen, that when the Mortise is empty of Seed, and the Tongue set up close, a Wheel might, in Turning, or otherwise, go a little backwards, and cause a Notch of the Spindle to take hold of the End of the Tongue, and tear it out of the Mortise: Therefore let the Tongue reach a little below the Spindle, as the pricked Line _g h_, in _Fig._ 3. of _Plate_ 2. doth.

As for the Posture in which the Tongue ought to stand in the Mortise, it is shewn by the Three pricked Lines in _Fig._ 3. _Plate_ 2. where the pricked Line _g h_ makes an Angle of Forty-five Degrees, being the nearest that it can stand to the Spindle; the pricked Line _i h_ makes a somewhat greater Angle, and it is a mean (or middle) Distance from the Spindle; and the pricked Line _k h_ is supposed to be its greatest Distance, where the Tongue makes its greatest Angle with the Top and Bottom of the Mortise. If the Tongue stood so obliquely as to make an Angle much less than Forty-Five, the Tongue would rise too much against the Bevel of the Mortise, and the Spring would have the greater Difficulty in returning it to its Place, when driven back by the Force of the Notches.

And beside, when the Tongue stood wide from the Spindle, there might be so much Room betwixt it and the Sides of the Mortise, that some Seeds might fall thro’ there.

The Steel Spring is D, properly placed upon the Back of the Tongue, in _Fig._ 1. _Plate_ 3.

At first, I made the Spring double, _i. e._ with Two Legs, in Imitation of that in the Organ, and fastened into its Tongue, much after the same manner as the Spring of the Organ is into its Tongue or Flap, which prevents the compressed Air from passing out of the Sound-board, except whilst the Key is thrust down by the Finger of the Player; but the Drill-spring requiring to be of a vastly greater Strength than that, I made it of Steel, of the Breadth of half an Inch, instead of Brass Wire: This performed very well, and several Drills are yet extant, that have only this Sort of Springs: Yet I found there was great Difficulty to set the Legs at their due Distance from each other; for their Seasoning would alter them from what they were, whilst the Steel was soft: They also took up too much Room in the upper Part of the Mortise. Then, to remedy these Inconveniencies, I made it single, with only one Leg, which by full Experience is found to be much better than the double one; it does not contain a Fourth Part of the Metal, and is most easily made, requiring none of that Trouble and Nicety that the double Spring doth. I shall therefore give a Description of the single Spring only.

B, the End of the Screw, which holds the Spring to the Tongue, thro’ a Hole near the upper End of the Spring; D, the Middle, against which the End of the Setting-screw bears.

Its Length is almost the whole Length of the Tongue; the End E reaching very near to the lower End of the Tongue, and the End B is as near the upper End of the Tongue; as it can be placed without touching the Cylinder of the Tongue.

The Breadth is usually about half an Inch; the Thickness must be in proportion to its other Dimensions, and according to the Degree of Stiffness required.