14 



PRINCIPLES 



OF 



V. I 



a bearing rein. These are all the parts really 

 necessary to constitute the curb. 



The bits thus formed being placed in the 

 mouth, and the chain passed round the lower 

 jaw, the branches, it will be readily seen, be- 

 come powerful levers when drawn backwards, 

 acting upon the mouth piece as a centre, and 

 squeezing, by means of the chain, whatever 

 interposes between it and the mouth piece, 

 with a force equal to the length of lever af- 

 forded by the lower branch. 



This force, it will be perceived, is regulated 

 not only by the length of the lever below the 

 mouth piece, but also by the greater or less 

 distance at which the chain is placed from it. 

 The chain is usually fixed to the eye of the 

 cheek piece, where the head stall is fastened : 

 if, therefore, this part is very long, it is evi- 

 dent it must moderate or counteract the power 

 and effect of the lower end of the branch, 

 and render it less severe, by bringing the 

 centre of motion nearer to the middle of the 

 lever. 



