410 



ON DRAUGHT. 



hovsp, are not onlv the most ancient, but still remain the most advantageous 

 source of power. 



L'jntJ- experience has pointed out the various modes of applying animal 

 power; but it is iVequetitly ill-directed, owing to the want of an adequate 

 knowled'fc of tiie meclianical structure of the animal, and the manner in 

 whicii lie exerts his strength. 



In the most powerful steam-engine, if too great a resistance be applied, 

 or, practically speaking, if we attempt to make it do more work than it is 

 calculated for, there is an immediate loss of power, in consequence of the 

 diminution of velocity caused thereby ; and if we continue to oppose a still 

 greater resistance, we reach the point at which it is unable to overcome it, 

 and it ceases to produce any effect. Again, a very small obstacle may be 

 so applied as greatly to- impede an engine of considerable power, or even 

 to stop it altogether. The power of an engine is limited, and resistance 

 must always be proportioned to it ; and there is a proportion beyond which 

 it is useless to go, and less than which would not absorb the whole force. 



An animal is but a beautiful piece of machinery, and altiiough perfect in 

 its construction, and wonderfully accommodating in its movements, it still, 

 like the engine, has a limited power, and has its peculiar modes of action, 

 its strong and its feeble parts; and we must well consider its structure, to 

 be able to apply the resistance in that degree, and in that manner which 

 shall enable it to produce the greatest effect. The consideration of the 

 comparative effects of the exertions of a man and a horse will at once 

 exemplify this, and lead us more clearly to the knowledge of the peculiar 

 qualities or faculties of the horse. 



If a horse be made to carry a heavy weight rapidly up a steep ascent, or 

 if a man be employed to drag slowly a heavy carriage along a rough road, 

 the strength of both will be soon exhausted, and little effect produced; 

 but if a man be made to carry a weight up a ladder, and if a horse draw a 

 heavy carriage along a road, they will each produce a considerable effect: 

 yet, in the former case, the horse and the man are as strong as in the latter, 

 but the power is not properly applied, and is consequently wasted. 



These different results are easily explained, by considering the mechan- 

 ical structure of the two bodies, and the mode in which their muscular 

 strength is exerted. 



^^/.2. 



The action of pulling is effected in either case by throwing the body 

 forward beyond the feet, which form the fulcrum, and allowing the weight 

 of the body, in its tendency to descend, to act against the resistance applied 

 horizontally, and drag it forward ; as the resistance yields, the feet are car- 

 Tied forward, and the action renewed, or rather continued. 



Let A {fig 1.) be the centre of gravity, or the point in wJiich the whole of 



