3 2 6 Of the Drill-Boxes. Chap. XX. 



and the Line a c, being joined to the Line b f in 

 Fig. 6. would be the End of that Notch in its pro- 

 per Poflure \ and then the Line b c, being an Arch 

 of the cylindrical Spindle, would be the Edge of the 

 upper End of the Notch, a b c, being the Area of 

 this End, is a Plane, and, when in its Place, makes 

 an Angle of Forty-five Degrees with the Axis of the 

 Spindle. The other End is the fame with this in all 

 refpecls, except that, being oppofite to it, it is in- 

 clined to it in an Angle of Ninety Degrees, at the 

 bottom Angle of the Notch, at the Line e f in 

 Fig. 6. 



Fig. 8. is a Notch lying with its Ends near it, and 

 is of the fame Dimenfions with thofe appearing in 

 the Seed-box, Fig. 3. 



The Cover B appears with its upper Surface rightly 

 placed in the Mortife, in Fig. 3. of Plate 3. where 

 its Breadth is fhewn to be the fame with that of the 

 Mortife •, but its Shape, and other Dimenfions, are 

 ted feen in Fig. 3. of Plate 2. where f t is its 

 Length, and reaches from the Hinder-end of the 

 Mortife, to within the Tenth of an Inch of the upper 

 End of the JxTs iranfuerfus of the Ellipfis ; its 

 greater!: Depth is from v to w 9 and is made fo deep, 

 that its Bottom, at w % bearing againft the End of 

 the Mortife, may prevent its Point, which is at /, 

 from finking down to touch the Spindle, which it 

 neither muft do, nor be fo high above it as to ftifTer 

 a Seed to pafs between the Spindle and it, tho' the Seed 

 is not apt to pafs that Way, becaufe the Notches throw 

 it forwards from the Cover, z is the Hole, thro' 

 which an Iron Screw-pin paries, and fcrews into the 

 oppofite Sides of the Mortife, to hold it firm in its 

 Place : 3 Tis made fo thin betwixt x and y both for 

 Lightnefs, and that the Seed may come the more 

 freely to the Notches, without Danger of Arching 

 at that End. Xhe Ufe of the Cover is to prevent any 

 Seed from falling down behind the Spindle. 



F& 



