3 i8 Of the Drill-Boxes. Chap. XX, 



to the neareft Part of the Hole, which will ever be 

 a perpendicular Line drawn from the Centre of the 

 Hole to the Place of PrefTure above-mentioned, and 

 make another Mark there : Now the Diftance be- 

 tween thefe Two Marks is the Meafure (near enough) 

 of the Tongue's Play at the Place of PrefTure. Tho 9 

 this Line drawn on the Side of the Mortife be not 

 exactly perpendicular to the Surface of the Tongue, 

 but only to its Edge -, yet the Difference is next to 

 nothing, and not to be regarded. 



If its Meafure be a quarter of an Inch, it is what 

 Experience fhews to be of a good Size for all Corn 

 and Peas; a little lefs is no Harm, but greater is the 

 mod fatal Error, into which moft of the Pretenders 

 to the making of this Machine have fallen; they give 

 the Tongue half an Inch, fometimes Three quarters 

 of an Inch Play. The Miichief of this Error is yet 

 farther increafed, if the Spring be weak, it the Mor- 

 tife have too great a Bevel, or if the Angle made by 

 the Tongue at the upper Edge of the Mortife be too 

 acute. 



When the Tongue has too great Play, the Sc^d 

 is apt to be turned out too fail, or elfe too lie y, 

 in fpite of the Driller. For when the Tongue is 

 let at its due Diftance from the Spindle, and is thruft 

 quite back by the Seed prefTed againft it by the 

 Turning of the Notches ; but the Spring being un- 

 able to return the Tongue to its former Place at fuch 

 a Diftance, at the time of pafling the Intervals which 

 are betwixt the Notches •, then the Space between the 

 Spindle and the Tongue being too open, the Seed is" 

 lent down too faft. 



To prevent that, they kt up the Tongue to the 

 Spindle ; and then, as often as the Spring happens 

 to overcome the Force of the Seed's PrefTure (as 

 fometimes it will),, it is fent out too flowly. 



The Inequality of the Running of the S^d makes 

 fuch Boxes ufelefs, which the Expence of Two-pence 



(for 



