182 BITS AND BITTING. 



portion destined to act on the tongue should be of 

 exactly the proper dimensions and form. Of course 

 there is a great difference in this respect between 

 smooth mouthpieces and such as have a port; in fact, 

 it is only as regards the latter that the dimensions are" 

 important. "Where, then, a port exists, its width should 

 be exactly that of the tongue-channel, as otherwise it 

 would either intrench on the space allotted to that 

 portion of the mouthpiece required for the bars, and 

 produce the inconveniences alluded to above ; or, if 

 narrowed, it would fail to answer the purpose for which 

 it is intended : namely, to admit the tongue.''' The 

 width of the port must he, therefore, exactly that of the 

 tongue-channel — and this is the second grand rule as 

 regards the mouthpiece. Now it has been already 

 shown that the width of the tongue-channel is very 

 constantly three-fourths of the height of the bars, 

 which, being equally constantly 1.8 inches, we have \\ 

 inches for the maximum width of the port, even in^ 

 cases where the total width of the mouth, and conse- 

 quently of the mouthpiece, amounts to 4J and S^V 

 English inches : for pony and hack bits, about 1 inch 

 will suffice ; whereas the common practice of the bit- 

 makers seems to be to make it one-third of the total' 

 width in all cases. 



For the height of the port, of course, no rule can be . 

 given, this being precisely the most variable dimension 

 of all, and depending altogether, so far as the interior- 

 conformation of the mouth is concerned, on the relative 

 thickness of the tongue and sensitiveness of the bars ;- 



* The Germans call the port of a bit the " tongue freedom" 

 — Zungenfrelheit — which expresses exactly the purpose for 

 which it is intended. 



