176 THE OLIVER PLOW BOOK 



power; although the law that the draft line will 

 straighten itself is just as true. 



A farmer can either separate his horses or bring 

 them closer together to approach more nearly the 

 straight line of draft. But the man who operates a 

 tractor has not this advantage. In order to approach 

 this line of draft, he must either run his tractor in the 

 furrow close to the furrow wall, or else permit of side 

 draft when plowing is difficult. 



Everyone knows that it requires a certain amount of 

 effort to produce a given result. Figuring energy and result 

 as weight, we can readily see that it will require a given 

 weight in energy to produce a given weight in result. 

 Carrying this illustration a step farther we know that 

 it requires one hundred pounds weight to balance one 

 hundred pounds on a fulcrum between the weights an 

 equal distance from each. Naturally then, if the greater 

 weight is the tractor the result will show on the plow, 

 but if the greater weight is the plow, the result will show 

 on the tractor; and where the weight is more equally 

 divided the result shows on both. 



Since the pressure against the mouldboard varies very 

 greatly in a given field, it should be apparent that when 

 the tractor begins to swerve to one side the plow is in a 

 hard condition of ground and naturally is exerting itself 

 to straighten the draft line by pulling the rear end of 

 the tractor around towards a point in the center draft 

 line. On the other hand, if the tractor is running 

 parallel to the plow wall and the plow is swerved to one 

 side it is plainly evident that the plowing conditions are 

 light. But in both instances the operator should know 

 that he is not approaching the draft line, and that the 

 plow and tractor are doing their utmost to observe this 



