THE PLOW IN GREAT BRITAIN 141 



knowledged him as the inventor of the moldboard founded on 

 mathematical principles. 



Jefferson demonstrated that the shaping of the moldboard 

 could be reduced to an exact basis, but his plow was defective 

 in many points. A diagonal drawn on the surface of the plow 

 from the point of the share to the tip of the overhang on the 

 moldboard was a straight line. At every point on the diagonal 

 an intersecting line touching the upper and lower edges of the 

 moldboard would have been straight. On a vertical section 

 of the moldboard, at any point except one, the line representing 

 the face of the moldboard would have formed the hypotenuse 

 of a right triangle if taken with the base line and a perpen- 

 dicular dropped from the upper edge of the moldboard. The 

 one exception is where points in the upper and lower edges 

 were in the same vertical line. The absence of curves made 

 it necessary to make the moldboard twice as wide as the furrow 

 to prevent the earth from surmounting it and falling behind 

 in the furrow. For the same reason it was necessary to make 

 the moldboard very long and the twist very gradual. 



This reduced moldboard friction in one way, but the long 

 bearing surface offset this advantage. It was impossible to 

 secure enough overhang to turn the furrow under all conditions 

 without making the share too blunt and the plow impractical 

 on account of draft. Small, in Scotland, had in the meantime 

 worked out by experiment the moldboard on his East Lothian 

 plow, which, when analyzed, is seen to have followed a curve 

 instead of a straight diagonal. This allowed a greater over- 

 hang, without too blunt a share, and the precise nature of the 

 curvature back of the centre of the moldboard reduced the 

 abrasion of the crest of the furrow, as previously noted. 



After Small, Mr. Wilkie, of Uddingstone near Glasgow, was 

 the next to alter the shape of the plow. His inventions were 

 embodied in the Lanarkshire plow, the moldboard of which 

 presented convex lines to the passage of the furrow slice, and 

 thus minimized the friction on the cherished crest. He also 



