AGRICULTUUAL E:N GIN BERING. 159 



EFFECT OF INCLINATION ON TRACTIVE FORCE. 



(U. S. Department of Agriculture.) 



The table gives the tractive force necessary to draMr i ton 

 over the best macadam road of various grades, and the 

 equivalent length of each mile of grade in miles of level 

 road. 



The effect of the inclination can be calculated from the 

 following formula: 



R = F^ alV, 



where F = force required to draw the load on the levels 

 a = the grade, expressed by a fraction, W^ the weight of 

 the load in pounds, R = force required to draw the load up 

 the incline in question. 



According to Gillespie, if a horse can pull on a level 

 1000 pounds, on a rise of 



I foot in 



100 feet he draws 900 lbs. 

 50 " •* " 810 " 

 44 " " " 750 " 

 40 " '* *• 720 " 

 30 •' •* " 640 " 



/ooi in 

 25 feet he draws 540 lbs. 

 24 " " " 500 " 

 20 •' '* " 400 " 

 JO " " '* 250 •' 



