542 



ON DRAUGHT. 



legs AB, is also proportion- 

 ably less than in the second 

 ease, where the traces are 

 horizontal. In fig. 6, where 

 the traces incline down- 

 wards, we see that the ho- 

 rizontal force AE is much 

 more considerable ; but, at 

 the same time, AB is in- 

 creased, and consequently 

 the muscular exertion re- 

 quired in the legs is pro- 

 portionately great ; in fact, 

 here a portion of the weight 

 of the load is transferred to his shoulders. 



The comparative advantages, 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 feelings, we will take the 

 case of a man. We have already seen that an able-bodied man is more 

 adapted for lifting than pulling ; consequently, in liis case, it would be 

 advantageous to throw a certain portion of the weight upon him, by making 

 him pull upwards, as in fig. 7, or what we are more accustomed to see^ and 



Fig. 7. 



which amounts to the same thing, applying his strength to a wheelbarrow, 

 fig. 8, and we have frequently seen an ordinary man wheel 800 lbs. in this 

 manner. 



If, however, we take a person unaccustomed to hard work, and con- 

 sequently not so strong in the legs, although he may be unable even to lift 

 the wheelbarrow which the other moved with ease, still he may, by pushing 

 horizontally, put in motion a considerable load ; and lastly, in the case 

 of an invalid who can barely carry his own weight, if he lean on the back 

 of a garden-chair, he will not only walk himself, but push on the chair ; 

 or a child who is yet too weak to stand, can, if part of his weight be 

 supported in a go-cart, not only move himself, but also the frame which 

 supports him. These are very familiar and homely comparisons, but they 

 are cases exactly similar to the three positions of the traces ; and the 

 argument ^vill equally apply to horses as to men. It is true, we rarely 

 use for draught a horse that cannot stand ; but the case is very possible 

 that a large heavy horse, otherwise not strong, or one which it was not 

 desirable to fatigue, might pull better and longer, if part of the weight 

 was borne upon the carriage, or if, in other words, the traces inclined 

 upwards. And we know by experience, tliat in the case of stage-coache?. 



