322 Of the Drill-Boxes. Chap. XX. 



middlemoft of the Three mentioned prick'd Lines. 

 This Setting-fcrew ought to be fmooth and round at 

 its End, which bears againft the Spring ; for, if it 

 mould have iharp Corners or Edges, the Spring 

 might be wounded by them, and in time might break 

 there, being prefs'd by every Notch that turns againft 

 it; and, as I have computed it, a Spring undergoes 

 One hundred thoufand of thefe Preftlires in one Day's 

 Work; and yet, in my whole Practice, I have had 

 only one Spring broken, and that was in drilling a 

 large Sort of Peas with a Wheat-drill, and was oc- 

 cafioned by a jagged End of die Setting-fcrew, 

 which was not placed perpendicular to the Spring* 

 by which means the rough End of the Screw made 

 Scratches againft it a Quarter of an Inch long, and 

 fo deep, that the Spring broke off there : Let not this 

 Setting-fcrew be any longer than juft to force the 

 Tongue up to the Spindle ; for, if it mould be longer, 

 an ignorant Driller might happen, by the Force of" 

 the Screw, to break the Tongue, or its Axis; but 

 in the Turnep-drill, which has only a Spring inftead 

 of a Tongue, the Setting-fcrew may be a Thread or 

 Two longer ; becaufe the Spring will yield a little to 

 ir, after it touches the Spindle, and is fometimes of 

 Ufe in that refpect, when the Notches are too large. 

 This Screw muft be of fuch a Bignefs, that it may 

 not be in Danger of bending ; for if it* mould be 

 bent, it could not be fcrew'd up with any Certainty, 

 becaufe its End, being crooked, would be below its 

 Place at one Half-turn, and above it at the other 

 Half-turn, and fo the Spring might be fet farther 

 from the Spindle inftead of nearer, and nearer in- 

 jftead of farther, by the Crookednefs of the Setting- 

 fcrew. Its Head may be made with a Notch in it, 

 to be fcrew'd in with a Knife, or eife with a Head 

 like a T$ to be turn'd with the Fingers, which I think 

 is beft, efpecially for a Wheat-drill; becaufe as the 

 Brine and Lime, which ftick on the Wheat, grow 



5 drier, 



