182 



ACTION OF A HORSE IN DRAUGHT 



CH. X 



«**. 



ciently, the vehicle will move forward as soon as 

 the horizontal force acting on the line is equal to 



the resistance to motion of the 

 vehicle. When the vehicle 

 moves in obedience to this 

 strain, the man is forced, in 

 order to avoid falling, to put 

 one foot in front of the other 

 and so successively to walk tor- 

 ward. As this strain upon the 

 line is produced entirely by the 

 weight of the man, it is evident 

 that the heavier he is the more 

 he can pull. The action of the horse is exactly 

 the same (Fig. 78), though at first sight it seems 



Fig. 77. 



Fig. 78. 



complicated by the fact of his having four legs in- 

 stead of two. As the vehicle moves in obedience 



