Chap. XX. Of the Drill- Boxes. 309 



the left Side of the Mortife ; the Areas of both being 

 true Planes {a). 



dikh Shew the Fore-end of the Mortife, mafk'd C. 

 dime fhew the Hinder-end of the Mortife, mark'd D. 

 a d h e fhew the Bottom of the Mortife already de- 

 fcribed in Fig. 1. If thefe oppofite Sides and Ends 

 were all raifed up, until the Angle at £join the Angle 

 at /, and that at m join /, and that at g join k, and 

 that /join f, the Top of the Mortife would be form- 

 ed, and the fame with the Parallelogram ab c d 9 in 

 Fig. 1. and then the intire Mortife of the Turnep 

 Seed-box would appear in its true Form, (landing 

 upon its Bottom. 



This differs from a common Mortife, in that it is 

 impoffible to fit it with a Tenon ; becaufe it is narrower 

 above, and fhorter below, as in Fig. 1 . 



The Areas, or imaginary Planes, of the Top and 

 Bottom of the Mortife, are parallel to each other, but 

 not equal. 



Its Two oppofite Sides are equal, but not parallel, 

 by reafon of their Inclination to each other upwards, 

 which is the Bevel hereafter to be defcribed. 



The Two Ends are neither parallel nor equal, be- 

 caufe the Hinder-end D is perpendicular to the Top 

 and Bottom, and the Fore^end oblique, and there- 

 fore longer. 



(a) Take care that thefe oppofite Sides be fare to be true 

 Planes, especially all that Part of their Areas, that is before the 

 tranfverfe Axes of their Ellipfes herein after defcribed ; for mould 

 they be otherwife, the Bevel of the Mortife would be fpoiled, 

 and fo would the Ellipfes, and the acute Triangles, on the Sides 

 of the Tongue ; which how neceffary they are to be true, is 

 fhewn in the proper Place. Workmen are very apt to fail in this 

 when they file by Hand, and make thefe Sides of the Mortife 

 convex inftead of plane. Therefore this might be done with 

 lefs Difficulty, and more Exadlnefs, with a File placed in a Frame, 

 whereby it might move upon a true Level without rifing or finking 

 of either End. 



X 3 When 



