Chap. XX. Of the Drill-Boxes. 3 3 7 



arrive at the lower End of the fame Axis, which is 

 below the Seed-pafTage, as its upper End is very near 

 the Cover. 



This Opening of thefe oppofite Semi-ellipfes 

 makes it impoflible for any thing, of itfelf, to get 

 into the remaining Parts of this hollow Cylinder, 

 betwixt them and the folid Cylinder, call'd the Spindle, 

 which turns continually therein, when the Wheels are 

 going : For you will fee, that if you make a Mark 

 on the Spindle* clofe to the Side of the Mortife, at 

 the upper End of the longeli Ax of the Ellipfe ; and 

 then turn the Spindle until this Mark come againft 

 the lower End of the fame Ax ; and there make an- 

 other Mark on the Spindle, clofe to the Side of the 

 Mortife; and draw a Line from one Mark to the other, 

 parallel to the Ax of the Spindle, which will be the 

 Meafure of that Part of the Bevel of the Diameter 

 of the Hole ; every Point in this Line will, by an 

 intire Revolution of the Spindle, generate a Circle, 

 which will cut the Ellipfe in Two Places, once on 

 the Forefide of its longed Axis, and once on the 

 Back-fide or hinder Half of it -, and that all thefe 

 Points, in this Surface of the Spindle, defcribed by 

 thefe Circles, will enter the Hole, by the faid hinder 

 Semi-ellipfe, as the Spindle there turns upwards (as 

 it always does.); and they will all again come out on 

 the fore Semi-ellipfe, as they defcend towards the 

 lower End of the faid Ax of the Ellipfe. 



As thefe Points thus come out of the Hole, or 

 (if I may uie the Expreflion) as they emerge, they 

 oppofe every thing that would enter the Hole, they 

 Hill moving from the Hole, and pufh away from it 

 whatever they meet; nay, if any thing were in the 

 Hole, thefe Points (whereof this Surface confifts) 

 would bring it out by this Semi-ellipfe, which is al- 

 ways prefs'd by the Seed when the Drill is at Work; 

 but as thefe Points immerge by the other Semi-ellipfis 

 which U behind the Spindle, they can carry wi:h 



Z them 



