CONSTRUCTION OF CURBS, 203 



port (see Fig. 23), has been devised, to throw more 

 pressure on the former than on the latter, in order to 

 increase the severity of the bit. 



Principles to be observed in the construction and adjust- 

 ment of curbs. — (i.) The longer the upper arms of the 

 cheeks of the bit (see Fig. 23) are, the greater will be 

 the downward pull on the headstall of the bridle, and 

 the more tendency will the curbchain have to mount up 

 on the sharp and sensitive edges of the branches of the 

 jaw. If, however, the upper arms be too short, they 

 will allow the cheeks of the bit to come in a line with 

 the reins, when the horse pulls, and, consequently, will 

 do away with all the mechanical advantage to be 

 derived from the employment of a curb. I have found 

 that, for ordinary horses, it is advisable to fix this length, 

 measuring from the lower edge of the mouthpiece (on 

 which the upper arms of the cheek revolve) to the 

 upper ring of the cheek, at ij inches (see Fig. 26). The 

 measurement is usually taken from the centre of the 

 mouthpiece, a plan which does not allow for the thick- 

 ness of this steel bar. It is evident, however, that the 

 thicker the mouthpiece, the longer does the upper arm 

 virtually become. 



(2.) Having now fixed the length of the upper arm of 



