492 Farm Mechanics. 



2.5 miles X 100 = n miles X Traction. 

 Thus at two miles per hour the traction would be: 



2.5 X 100 2 X Traction, 

 whence Traction = * a or 123 Ibs. 



613. Diminishing the Number of Hours Per Day Increases 

 the Power of Traction. When the speed remains the same 

 experience has shown that, between 5 and 10 hours per day, 

 diminishing the time increases the possible traction in 

 about the same ratio, or 



10 hours X 100 = n hours X Traction. 



Thus, if the horse is to be worked only 5 hours the trac- 

 tion he may exert will be 



10 X 100 = 5 X Traction, 

 whence Traction = u** = 200 Ibs. 



PRINCIPLES UNDERLYING THE DRAFT OF THE HORSE. 



The principles governing the draft of a wagon have been 

 discussed in Chapter XX j there are others affecting the 

 horse as a motor which need to be considered here. 



614. Direction of the Line of Draft. When a horse has 

 a muscular development and a type of skeleton which per- 

 mits him to utilize his full weight in hauling then the di- 

 rection of the line of draft, or of the traces in pulling, ex- 

 erts an important influence upon how much the horse can 

 draw. In Fig. 235 is represented an apparatus for dem- 

 onstrating this and other principles underlying the draft 

 of the horse. 



When the line of draft is horizontal, as represented in 

 the figure, the spring balance will register a tension on the 

 traces nearly equal to the weight of the model when the 



