56 Report on Trials of Plows. 



of an inch above the plane of the sole, as at the dotted lines, mz, 

 in Fig. 126. The lower edo;e of the mould-board is also to be 

 rounded off as shown by the dotted lines along the lower edge 

 from h to o, Fig. 128. To prevent the abrasion of the edge of 

 the slice in passing over the mould-board, it will also be expedient 

 to make the lines from d to il in Fig. 126, fall in from below the 

 line of transit upward, as shown in the dotted lines at d' a' h' «." 



In order to complete this sul)ject for the benefit of plow-makers, 

 we give Mr. Stephens' method of forming the pattern of a mould- 

 l)oard, practically, as we have already given them theoretically. 



The Mould-board Pattern. — In this operation the quadrant of 

 a cylinder, upon which the principle is founded, may or may not 

 be prepared. If it is to be employed, then the first process is 

 exactly as before descril)ed in reference to the quadrant, Fig. 123, 

 Plate IV, which must be formed and lined as there described ; but 

 the same process may be pursued by lines alone, without the 

 intervention of a solid, and in the following manner : Having 

 described the quadrant of a circle, as a 6 c. Fig. 123, of ten inches 

 radius, construct the diagram. Fig. 124, as before directed, the 

 entire length, e b, being thirty inches, divided into equal parts of 

 three inches each. The arc, b d, is then to be drawn through the 

 points b, p, n, m, which points, instead of being a transfer, as 

 before described, from the quadrant, may be drawn directly by a 

 beam compass touching the three leading points, b m d, as before, 

 which will intersect all the divisions, converting them into ordi- 

 uates, If, 2^, 3/?, etc., to the curve, b d. The lengths of these 

 ordinates from the base line, e b, are now to be carefully trans- 

 ferred to the quadrant of the circle, b d, of Fig. 126, and set ofl" 

 in the circumference thereof; thus, the point b, in Fig. 126, cor- 

 responds to the termination, b, of the l)ase line in Fig. 124. The 

 first ordinate, q j^, i'^ to be set ofl:' on the quadrant from b to j) ,' 

 the second ordinate, 8;^, is set off" from b to n ; the third, lin, 

 from h to m, and so on through the entire quadrant of the circle. 

 'Jhe radii, a b, a p, a n, etc., being now drawn, will furnish the 

 successive angles of elevation, with the sole plane for each divisi(ni 

 of the length throughout the quadrant. 



lu. applying these to the mould-board, it is to be observed that 

 the first three radii belong to the share, if it is a prolonged mould- 

 board ; or the first five, if it l)e truncated. The quadrant, Fig. 

 126, with its radii being tluis completely drawn out at full size 

 upon a b(»:u(I, produce Ihe line b a to //, and on y, as a centre 



