Chap. XX. Of the Drill-Boxes. 3 2 1 



The Degree of its Stiffnefs is known by weighing, 

 as has been directed for the other Spring •, and being 

 laid with its Face downwards over a Chink, with a 

 fmall Piece of Wood of the Thicknefs of a Barley- 

 corn at Each end, and a String taking hold of its 

 Middle, and defending thro' the Chink, the Weight 

 of Five Pounds, tied to the End of the String, will 

 juft bend the Spring* till it touch the Edges of the 

 Chink ; and this is the Stiffnefs of a Spring that has 

 performed well, for many Years, in drilling of Tur- 

 nep-feed. 



The Setting-Screw. 



Fig. 6. is the Iron Setting-fcrew, which paffes 

 thro' the Hole in the Fore-end of the Mortife, Fig. t. 

 and paffes up to the Middle of the Spring by the 

 prick'd Line p q in the fame Figure. The Ufe of 

 this Setting-fcrew is, to increafe or diminifh the Pro- 

 portion of Seed to be turned out by the Notches ; 

 and this it does by forcing up the Spring and Tongue 

 (where there is one) nearer to, or farther from the 

 Spindle, whereby the Seed-paffage is made wider of 

 narrower, as is fhewn by the Three prick'd Lines in 

 Fig. 2. and Fig. 3. 



Obferve, that the prick'd Line p q, Fig. 2. (being 

 the Mortife of the Turnep-box) Hands higher than 

 the fame Line doth in Fig. 3. v/hich is the Mortife of 

 the Wheat-box. The Reafon of this Difference is, 

 becaufe the Spring in the Wheat-box bears at its lower 

 End againft the Tongue below the Seed-paffage, and 

 at its upper End below the Axis of the Tongue, 

 whereby the Middle of that Spring is lower than the 

 Spring of the Turnep-box, v/hich, being both Spring 

 and Tongue, bears againft its Axis above, and agaimt 

 the Seed-paffage below; therefore its Middle is higher. 

 This Setting-fcrew mould be placed perpendicular to 

 the Tongue when at its mean or middle Didance 

 from the Spindle, which may be fuppofed to be the 



Y mi c die- 



