418 



ON DRAUGHT. 



iheir lurn, in den"^nstrating the correctness of their own theory, proved 

 the error of others, there can be no presumption in laying them all aside, 

 and in taking a different, but at the same time a more simple and pr^ictical 

 view of the case. By referring to a figure, similar to that by which we 

 showed the mode of action of the horse in pulling, we see that if AD 

 represent that portion of his whole weight which is relieved from his fore- 

 legs, and AE the direction of the traces, then AF is the measure of the 

 horizontal pull upon the carriage. Now, AF bears a constant proportion 

 to AB, which represents the strain upon the legs; and AD being constant, 

 AB, and, consequently, AF, increase or diminish according as the angle 

 ADB is increased or diminished : that is to say, the horizontal pull applied 

 to the carriage is proportionate to the strain upon the legs; but they are 

 both dependent upon the angle formed by the traces, increasing or dimin- 

 ishing as the latter are 

 Fig- 4. inclined downwards or 



upwards from the collar ; 

 so that whether the traces 

 be inclined upwards, aa 

 jig. 4, or downwards, at 

 Jig. 6, or whether the) 

 be horizontal, as jig. 5, 

 makes no difference in 

 the manner of pulling. 

 In the first case, a por- 

 tion of the animal's 

 weight is borne by the 

 traces, and is transferred 

 by them to the carriage. 

 AF is here small, but the 

 strain upon the legs, AB, 

 is also proportionably 

 less than in the second 

 case, where the traces are 

 horizontal. In jgure 6, 

 where the traces incline 

 downwards, we see thai 

 the horizontal force, AE, 

 is much more consider- 

 able; but, at the same 

 time, AB is increased, 

 and, consequently, the 

 muscular exertion re- 

 quired in the legs is pro 

 portionably great. In 

 fact, here a portion of the 

 weight of the load is 

 transferred to his shoul- 

 ders. 



The comparative ad- 

 vantages therefore of the 

 three do not follow any 

 general rule, but depend 

 simply upon the peculiai 

 qualities of the particu- 

 lar animal employed, and his relative capabilities for lifting and pulling, 



