DRAFT OF PLOWS 211 



ing the line of draft as it encounters obstructions. Practically 

 it is shown to save from 9 to 14 per cent, by the steadier running 

 of the plow when it, and not the handles, is used to regulate the 

 depth. 



The power absorbed in severing the furrow slice demands 

 that shares be not only sharp but properly sharpened. San- 

 born reports a difference of only 6.7 per cent, in favor of an old 

 point resharpened over a dull point on the same plow, but an 

 advantage of 36 per cent, in favor of a new point over the old 

 one resharpened. A straight edge drawn across the share at 

 a right angle to the landside should touch for an inch or so on 

 the under side of the cutting edge. The average blacksmith 

 will hardly restore to a share the nice adjustment given it at 

 the factory, and it is an open question whether a farmer can 

 long afford to waste power on resharpened shares. Sanborn 

 states that in the case quoted the defects were not easily dis- 

 cernible and the work compared favorably with that of the 

 average smith. 



At all events, the farmer should not waste power on dull 

 shares. 



At the Winnipeg motor competition hi 1909 two six-bottom 

 engine gangs of the same make, supposed to be cutting the 

 same depth and width, showed a difference in draft of 45 per 

 cent. Most of this can be attributed to the fact that one 

 was a new plow, just from the factory, especially ground for 

 the occasion, while the other had been used for several months 

 for plowing in stony ground, with only ordinary attention. 



Speed of travel as a factor of draft is an unsettled question. 

 Theoretically, the resistance should increase in a definite ratio 

 with the velocity, as in case of bodies moving through air and 

 water. Practically, within the ordinary limits of speed, the 

 higher rate is considered by some to decrease draft by inducing 

 better scouring and turning of the soil by the moldboard, es- 

 pecially in heavy soils. Gould's experiments at Utica resulted 

 in the conclusion , that in plowing friction is entirely indepen- 



