THE ANGLE OP TRACTION, ETC. 229 



trace / e (compare Fig. 17 a) forms a still greater angle, 

 and the tendency of both must always be to lift the 

 collar upwards, the evil effects of which we have shown. 

 But with the draught-bar in the centre of the leg of the 

 hames, we have both the long and the short traces, d c 

 and d e, in the line of the bar, and both, therefore, 

 causing a perpendicular pressure of the whole under- 

 surface of the collar on the horse's shoulder. 



The Trace. There remains nothing to be said of the 

 trace, excepting what regards its length. In England 

 horses are harnessed much shorter and nearer to their 

 work than in any other country. Some of the reasons 

 for this are sound and practical, others simply mistakes 

 or misapplied forms of correct general principles. It is 

 in the first place possible to use very short traces in this 

 country, because our roads are very generally superior 

 to any others; then it is always desirable when the 

 work is to be done on crowded roads or streets with 

 frequent stoppages and sharp turnings. Even for 

 military purposes, where much of the work must be 

 done on difficult ground, there is an advantage in 

 making the teams as short as is otherwise consistent 

 with the ease of the horses, because the length of 

 the columns is thereby kept within limits. But it is 

 altogether a mistake to suppose that a short trace of 

 itself confers a greater mechanical advantage on the 

 motor (horse) than a longer one ; in fact, it is very evident 

 that the contrary may be the case, for Figs. 19 and 20 

 show very plainly that the angle of traction may be 

 made more favourable with a long than with a short 

 trace ; and what is true with regard to the inclination 

 to the horizon is equally so with regard to a line 

 representing the axis of a carriage. In fact the well- 



