532 



ON DRAUGHT 



been advanced ; some having recommended it to be horizontal, others inclined ; 

 and, as they have each in their turn, in demonstrating 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 practical 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 repre- 

 sent 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 repre- 

 sents 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 diminishing as the latter are inclined downwards or up- 

 wards from the collar; so 

 that whether the traces be 

 inclined upwards, as fig. 4, 

 or downwards, as fig. 6, or 

 whether they be horizontal, 

 as fig. 5, makes no difference 

 in the manner of pulling. 

 In the first case, a portion 

 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 proportion- 

 ably less than in the second 

 case, where the traces are 

 horizontal. In fig. 6, where 

 the traces incline down- 

 wards, we see that the 

 horizontal force AE is 

 much more considerable ; 

 but, at the same time, AB 

 is increased, and conse- 

 quently the muscular ex- 

 ertion required in the legs 

 is proportionably great : in 

 fact, here a portion of the 

 weight of the load is trans- 

 ferred to his shoulders. 



The comparative advan- 

 tages, therefore, of the three 

 do not follow any general 

 rule, but depend simply 

 upon the peculiar qualities 

 of the particular animal 

 employed, and his relative 

 capabilities of lifting and 

 pulling, or the proportion 

 existing between the weight 

 of his body and his muscular strength. To render this more clear to our own 



