30 Report on Trials of Plows. 



along the traces to the line o h, at the rear, and the line d /, in 

 front, the fore part of the saw will come out on the face, a m d, 

 as we go on towards c, at constantly varying elevations above the 

 line a m. If we now connect the points thus made by the saw on 

 the face, a m d, the line traced between them will be the line 

 '; f/ d, Figs. 24 and 25. Beyond this height the saw, directed in 

 the same manner, will come out at other points situated on the 

 posterior face, a b m I, and a line connecting these points, as 

 before, will form the second of these curves on both figs., n, ?, 

 which will meet the first in the point n. 



These two curves being traced out, let us sui:)pose straight lines 

 drawn to the places where the saw stopped each time that it 

 touched the diagonal, d I, and of which one, as already said, passes 

 through the points s w y; and let us conceive a surface touching 

 all these straight lines, and w^hose limits, on the one hand, shall 

 be the curves d y n, I n, and on the other the line o //., this sur- 

 face, which must be uncovered by sections made with a proper 

 instrument, will form one of the faces of the mould-hoard, which 

 is represented hj d n I o c, Fig. 25, where c y represents the per- 

 pendicular and the point d curves over towards the spectator four 

 and a half inches beyond the point c. The share, I o x, has been 

 added to show how the plow looks when finished. 



To make the opposite face of the mould-board, the thickness 

 thereof having been determined by the thickness of d e k i, Fig. 

 24, at one and a half inches, let us first conceive that there has 

 ])een traced out, proceeding from the points, the cuvve c u p, 

 ])arallel to d y n, and then proceeding from the pointy, the curve 

 ]) q, parallel to n I. 



Let us next suppose that the saw cuts the edge h I of the face 

 h ami in the point cc', situated in the same plane as z x, t s, which 

 plane has been taken, for example, in regard to the anterior face 

 of the mould-board. The saw must be directed along the traces 

 x' z and x' s, in such a manner that its motion shall stop at the 

 term where its edge, on the one hand, shall touch the curve e p, 

 in the point v, situated on the trace x z, and, on the other, shall 

 be situated parallel to the line s w ?/, at which the saw stopped 

 on the other side of the mould-board. The edge of the saw will 

 then cut the face oi b I o c, in some point t ', so situated that the 

 straight line drawn through that point and the point w, shall be 

 parallel to the straight line which passes through the point s lo y. 

 If you continue cutting in the same manner, with the saw, differ- 



