The Cover B appears with its upper Surface rightly placed in the Mortise, in _Fig._ 3. of _Plate_ 3. where its Breadth is shewn to be the same with that of the Mortise; but its Shape, and other Dimensions, are best seen in _Fig._ 3. of _Plate_ 2. where _s t_ is its Length, and reaches from the Hinder-end of the Mortise, to within the Tenth of an Inch of the upper End of the _Axis transversus_ of the Ellipsis; its greatest Depth is from _v_ to _w_, and is made so deep, that its Bottom, at _w_, bearing against the End of the Mortise, may prevent its Point, which is at _t_, from sinking down to touch the Spindle, which it neither must do, nor be so high above it as to suffer a Seed to pass between the Spindle and it, tho’ the Seed is not apt to pass that Way, because the Notches throw it forwards from the Cover. _z_ is the Hole, thro’ which an Iron Screw-pin passes, and screws into the opposite Sides of the Mortise, to hold it firm in its Place: ’Tis made so thin betwixt _x_ and _y_ both for Lightness, and that the Seed may come the more freely to the Notches, without Danger of Arching at that End. The Use of the _Cover_ is to prevent any Seed from falling down behind the Spindle. _Fig._ 10. _Plate_ 2. is the Fore-end of a Wheat Mortise, with its Hole A, thro’ which the Setting-screw is screw’d, and passes up to the Back of the Tongue by the Line _q r_ in _Fig._ 3. _Fig._ 9. in _Plate_ 3. is the hinder End of a Wheat Mortise, which by its prick’d Lines, and the Two right-angled Triangles they make, shews the Bevel of the Mortise, and also its Depth; it also shews the Difference of the Bevel of the Mortise, and that of the Tongue, _Fig._ 1. which is placed against it: These Figures having been already demonstrated in the Description of the Turnep Mortise, and in these, I need say no more of it, but that I think these last-mention’d Figures sufficient Directions for understanding and making the Mortise of a Wheat-drill. _Fig._ 3. of _Plate_ 3. exhibits to View a Wheat Seed-box, with its Appurtenances, standing upon its Bottom; B the Brass Cover; C the Tongue hanging upon its Axis; _c_ the End of the Iron Screw that holds on the Spring, coming thro’ the Tongue, and filed smooth with it; _a_, _a_, _a_, are Three Notches of the Spindle, with their bevel Ends; _b_, _b_, are Two Interstices betwixt the Notches.