266 COUPLING CH. XII 



and B are the two sides of the off horse's bit, C and 

 D those of the near horse. The drauofht-reins AM 

 and DN run straight to the coachman's hand. The 

 coupling-reins are BN and CM, buckled to the 

 draught-reins at N and M. 



Now, if the off horse bends his neck so as to 

 bring his head nearer to his body, both the reins 

 which run to his bit will be too slack, and he will 

 run forward and do more than his share of the 

 work, while the near horse is held back. To 

 prevent this, the off horse's coupling-rein BX is 

 shortened by running it up the draught-rein to X', 

 the last hole, until it comes just tight to the bit ; 

 but this obviously leaves the off draught-rein AM, 

 as slack as it was before, so that the coachman has 

 to draw his hand back to bring it to bear upon the 

 bit at A'. In so doing, however, he draws back the 

 coupling-rein CM, and pulls the head of the near 

 horse to the inside. To prevent this, the coupling- 

 rein CM must be let out on its draught-rein exactly 

 as much as the other coupling-rein has been taken 

 up, which is equivalent to pulling back the draught- 

 rein, whereupon the coupling-reins will have the 

 positions shown by the dotted lines, with the buckle 

 of C rein in the first hole, and all the reins will act 

 evenly on both horses, notwithstanding that the 

 mouth and bit of the off horse is nearer to the 

 coachman's hand than that of the near horse. 



If the horses are too far apart, but otherwise are ' 

 working evenly, the coupling-reins must be short- 



