It is with reluctance I intrude Myself upon your attention, but as it is upon a Subject of Importance to Mankind, I hope I shall be excused.    It was with great Pleasure I read in a public print, last Summer, a part of a Letter of Yours to John Sincquair, President of the Board of Agriculture at London, Dated March 23rd, 1798 containing a Description of a Mould Board of a Plough, of your Inventing.

At that time I had frequent opportunities of using Ploughs of common Construction and was so sensible of the want of improvement in them, that I had formed a scheme in my Mind of effecting it. which scheme I shall here attempt to describe. The Share to be as wide as the intended width of the furrow, and about 2 Inches longer than it is wide, its edge from the [. . . .]int to the fin nearly strait, and sharp; the height of the back part of the share on the Left hand side 2 Inches; & the upper surface quite flat.

The Mould Board to be coincident with the Share where they join; its right lower edge to be parallel with the left side of the Plough; The form of the surface of the Mould Board is such as to act in the Manner of a Wedge, pressing at right angles to the underside of the Sod from the time it receives it from the Share, till it has carried it so far, that it will fall over by its own weight. The right lower edge being a strait level line, that side of the sod is not raised at all; & the left edge a spiral Line, all parts of which is equally distant from the left edge, winding, regularly, from the left side of the share, backwards, till it has passed beyond a perpendicular to the right edge.

Since reading the description of your Mould board in the above-mentioned Letter, I have thought that a Mould Board might be made, partly upon your plan, & partly upon mine, which would be better than either alone; from this Consideration, that the nearer the Sod approaches a perpendicular position, on its edge, the less is the force required to move it farther.   Now I conceive that if several equidistant planes were supposed to pass through the Mould Board, at right to the Line of the Ploughs Motion, the surface of the Mould Board, upon my plan, would mark lines upon these planes, which when all reffered to one, is represented by Figure 1, and upon your plan, by Figure 2, the first dividing an Arch equally (whose center is in all the angular points; being the right edge of the Mould Board;) the second dividing a Chord of 90 Degrees into equal parts, (this Chord may be supposed to be the Diagonal, drawn upon the upper face of your wedge,) of course in the first forming equal angles with each other, and in the second unequal angles, those in the Middle being the greatest.

GRAPHIC IN MANUSCRIPT

The increase of the angles in Fig 2, from the begining to 45 Degrees with the level line, I think is much better than the equal angles of Fig 1; but their decrease from thence, to, & beyond the perpendicular, I conceive to be a disadvantage, inasmuch as it increases the length of the Plough, or else makes it raise the Sod more suddenly at first.   I therefore now propose to divide the Sine of 45 Deg. a b (Fig 3) into equal parts, & the arch c d into parts each equal to the arch g c, and form a Mould Board according to this plan. I have not at present an opportunity of putting these plans in practise; but I have made a Modell upon a small scale upon your plan, & another upon that of Fig 3. & allmost every Person that has seen them thinks they are both much superior to the common Ploughs, but that the latter is the Best.

I should be happy to have your opinion upon these plans, and also to know what shape you would recommend for the Share, I have thought that that I have described is as good as any; but I submit it to your Judgement, whether, the form of the Mould board continued forward to a sharp edge, & then the Right Corner taken off, & the surface bevilled till it becomes a sharp edge, would be a better form.

With respect to making the Mould boards of Cast Iron, I think it an excellent plan, as they by that means may be made so exact, easy, cheap & Durable; & if well supported by the Wood-work, would in my opinion do for any kind of Soil; except where there were a many large Stones.

It is with the Greatest Pleasure I have heard of the Cheif Magistrate of a Great Nation lending his assistance in the forming the Instruments of Husbandry, & raises in Mind an Idea of your true Greatness, that your are far above the silly vulgar prejudice of thinking it beneath your dignity to be aiding in producing food for Mankind. It is my earnest wish, that each of your Fellow Citizens may possess the same exalted Mind laying aside the Love of Luxury, Pomp, Indolence & every other vice which tends to destroy the Happiness of themselves & their Fellow Creatures; studying the Works of their Creator & the best Means of promoting universal Happiness.

I Beg you to accept assurances of my Veneration & Esteem, and that you may long live to shew a bright example of unshaken virtue in the earnest prayer of your Admirer,