418 



ON DRAUGHT. 



y^ 



Fig, 5. 



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 

 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 propor- 

 tion 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, increas- 

 ing or diminishing^ as the latter are inclined downwards or upwards from 

 P^' 4. the collar ; so that 



whether the traces be 

 inclined upwards, as 

 Jig. 4, or downwards, 

 as fig. 6, or whether 

 they be horizontal, as 

 fig. 5, makes no dif- 

 ference 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 con- 

 siderable; but, at the 

 same time, AB is in- 

 creased, and conse- 

 quently the muscular 

 exertion required in 

 the legs is proportion- 

 ably great : in fact, here 

 a portion of the weight 

 of the load is trans- 

 ferred to his shoulders. 

 The comparative ad- 

 vantages, therefore, of 

 the three, do not fol- 

 low any general rule, 

 but depend simply 

 upon the peculiar 

 qualities of the parti- 

 culai animal employed, and his relative capabilities of Ufting and pulling, 



Fig. 6. 



