244 DEAUGHT AND HAENESS. 



obstacle to exist, never be at right angles to M, the 

 advantage with a wheel of a given height will always 

 be greater when the line of traction lies nearer Q 

 than to H — that is to sa}^ when the traction takes 

 place under an angle with the horizon. 



On the other hand, we have seen that with a sixteen- 

 hand horse, a horizontal trace is equivalent to a wheel 

 of 7 feet 4 inches is diameter, a dimension quite un- 

 suited to ordinary purposes ; and although such a wheel 

 w^ould surmount an obstacle of a given height more 

 easily than a 5-foot wheel, there would be a loss of 

 power, or rather an unnecessary expenditure of it 

 demanded from the horse, because the effort could not 

 be made in the direction Q, and therefore the sixteen 

 hand horse would experience less fatigue when work- 

 ing 0-foot wheels than with the otherwise more power- 

 ful 7 foot 4 inch ones, and least of all, of course, when 

 his traces were attached to the middle of the hames, 

 not only because this would bring the line of traction 

 nearer to Q, but also and mainly because it would 

 suit his own conformation and the mechanism of his 

 movements better. 



In order to wind this matter up, let us remind our 

 readers of one more very simple and familiar fact — 

 namely, that plough-horses do all their work under a 

 very considerable angle of traction, and in this case 

 there was no wheel to mislead people Avith Will-o'-the- 

 Wisp theories, or at least not until lately. 



There is one other point in connexion with wheels 

 to which we desire to call attention, because this too is 

 frequently misunderstood. It is said that, with a four- 

 wheeled A^ehicle, the load should be put as far forward 

 as possible, and that a man placed at the hinder end of 



