_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.