Supplementary Plow Trials. 



279 



It appears from the foregoing that, when the speed on the 

 second trial was very nearly doubled, the draught was only 

 increased 15i pounds, which was probably due to inequalities in 

 the soil; and when, in the third trial, the speed was again more than 

 doubled, the draught was only increased 180 pounds. It may be 

 considered as fully settled that velocity has very little influence 

 on draught. The last experiment does, indeed, show that the 

 draught was somewhat increased, and this was also the case in the 

 experiments of Messrs. Morton and Pusey; but the cause of this 

 increase was very apparent in our trials; and we have no doubt 

 that it was also the case in theirs. When the speed rose to 

 five and one-half miles an hour (nearly), the soil was thrown 

 upwards thirty inches high, and laterally four feet, so that four 

 of the preceding furrows were covered with pulverized earth. It 

 was this upward and lateral throw of the earth which consumed 

 the 180 pounds of power. So long as the speed is not increased 

 to the point where the earth is thrown upward and laterally, we 

 think it is demonstrated beyond all possibility of doubt that the 

 power required in plowing is not increased by an increase of 

 speed. 



IV. What proportion of the total amount of power consumed 

 in plowing is absorbed by the dilferent parts of the plow, viz., 

 the sole, the land side, the share, the mould board ? 



Exjieriment JVb. 38. — The surface draught of No. 65 (weight, 

 130 pounds) was 78 pounds. 



Experiment iVb. 15. — The surface draught of No. 69 (weight, 

 140 pounds) was 118 pounds. 



The greater surface draught of the latter was probably owing 

 to the greater breadth of the sole, measured from the laud side 

 to the angle of the feather. 



The average draught of No. 65, plowing seven inches deep, as 

 shown in experiments Nos. 49, 50 and 51, was 512 pounds. 



