142 POWER AND THE PLOW 



raised the heel, or rear corner, of the share above the point. 

 Thus he produced a furrow of trapezoidal section, partially 

 to reduce the draft, but mainly to secure a sharper angle to 

 the crest. These features are still in vogue and this plow has 

 always been a close rival of the East Lothian among farmers 

 who wish to see their furrows stand like saw-teeth. For plow- 

 ing matches in Eastern Canada, even in late years, manu- 

 facturers have built special plows incorporating these features, 

 though plows for general use have conformed more closely to 

 modern practice. 



Early in the century Stephens, in his "Book of the Farm," 

 gave a mathematical method of shaping the moldboard. This 

 was similar to Jefferson's, but by using the arc of a circle to 

 generate the surface lines, instead of a straight diagonal, he 

 produced a greater overhang at the rear and an easier slope 

 in front. He conceived of the furrow slice as a right prism, 

 elastic enough to yield to the passing form of the plow, and 

 tenacious enough to resume its shape when laid in position. 

 The slice must be turned on the lower right-hand edge as an 

 axis through an arc of 90 degrees, then on what was the upper 

 right-hand edge, through 45 degrees more, leaving it on a 45- 

 degree slant instead of completely inverting it. To accomplish 

 this he proposed a wedge, twisted on its upper surface, and to 

 find the form and dimensions of this wedge was, in his mind, 

 to solve the problem of the shape of the moldboard. His 

 plow was the first on which the neck of the share was elim^ 

 inated, the moldboard extending forward to form an angle 

 with the heel of the share. In this respect, and in making the 

 share cut the full width of the furrow, his plow still further 

 resembled modern American practice. He advocated the 

 use of malleable in place of cast iron for the moldboard by 

 reason of its resistance to shocks, though pointing out the 

 increased cost. The ideas worked out in Scotland by Small, 

 Stephens, and Wilkie have influenced the design of plows to 

 the present day. 



