112 



Report on Trials of Plows. 



said measurements being taken at the respective distances marked 

 on the perpendicular; the line m n is drawn in the plane of the 

 base of the mould-board, and the numbers from the perpendicu- 

 lars drawn from the line give the outline of the lower side of the 

 end of the board, and also of the top of it us far as the lin-; op; 



Fig. 69. 



and the measurements from the line p ?', drawn through the point 

 p, parallel to the plane of the base ot the board, gives its remain- 

 ing outline to the sheath (generally called the standard). The 

 line n b' c' p is a guide line in forming the face of the board. The 

 curve, b c h, may be determined bv the scale of one and a half 

 inches to the foot, which is that to which the respective figures 

 showing the parts in details are drawn. The face of the mould- 

 board was exactly perpendicular, and the line o jj from 5- to p is 

 in it; o p is also one of the guide lines in forming the face of the 

 board. The rise of the line of the board from a' to t' is made at 

 such a rate, compared with the spread of the board, as will exactly 

 preserve through that distance the same width of the plow as at 

 the heel, a'. From t' to the perpendicular the rise is such that 

 the increased width of the plow (Fig. 6S) is to the distance as 

 one to two and one quarter inches, and from the perpendicular to 

 the end of the board these measurements are as one to one. The 

 point, t', being where the action of the farrow slice, following 

 that of the heel,«', commences, I make that a point through which 

 to draw a line from the point of the mould-board, «, to the per- 

 pendicular. This line also lies in the surface of the board, and as 



