THE ANGLE OF TRACTION, ETC. 231 



of n is almost always adopted. Mathematically, or 

 what is the same thing, mechanically considered, m 

 and n are identical in their action, for although the 

 scroll may appear to work from two separate points, 

 this is merely apparent, and its action is in reality 

 precisely similar or equivalent to that of the bar m. 



Our plan being to point out defects, in the first in- 

 stance, instead of laying down dogmatically how things 

 should be, we would beg of the reader to consider for 

 a moment whether it is not really very remarkable 

 that, whilst the mathematicians and the practical men 

 all insist on the trace being adjusted so as to work hori- 

 zontally, the constructors of hames should always place 

 the bar m or the scroll n as if the pull were to be ex- 

 erted at right angles to the leg of the hames, through 

 this to the collar, and finally to the horse's shoulder 

 blade ; and as this latter is never, or at least only in 

 very miserably built horses, quite perpendicular, it fol- 

 lows that the horizontal trace must always act at an 

 angle on the bar m or scroll ?i, instead of on the pro- 

 longation of their axis, thus converting these contri- 

 vances into levers for grinding the collar obliquely into 

 the horse's neck or shoulder, instead of pressing it quite 

 flatly and equably against it. In fact, the hames makers 

 are evidently of our opinion, that the trace should al- 

 ways work at right angles to the shoulder-blade ; where 

 they do too often differ from us is, in placing the bar 

 m, or scroll 92, at the lower third instead of in the 

 middle of the leg of the hames. Let a h, fig. 19, 

 represent a hames, and p /, p d the draught-bar, 

 placed, in the former case, near its lower extremity ; in 

 the latter, in the centre of the line a b. The horizon- 

 tal long trace/c H forms, with the draught-bar at /, an 



