41 ^ ON DRAUGHT. 



An orrangement of this sort is, indeed, sometimes made use of, for rais- 

 in<f ihe earth from excavations, or the materials of a building ; but the 

 exertion is continued only for a few seconds, or for a distance of not more 

 than ten or twenty yards ; if prolonged, tiie inconvenience would be seri- 

 ously lelt, as it is, to a certain degree, in towing canal boats ; the length 

 and curve of the rope give an elasticity to the strain, and tlie necessity of 

 keeping llie rope out of the water, or from dragging along the towing-plth, 

 compels the animal to keep up a constant, unremitted pull, and that, too, in 

 an oblique direction, so as to throw him into an unfavourable position. We 

 accordingly find that, under these circumstances, the average work of a 

 horse is equivalent only to about four-fifths of that given by Smeaton, De- 

 sagudliers, and others, who estimated the power of a horse from the work 

 done in a horse-mill, where the resistance is inelastic, and all circumstances 

 favourable, with the exception of the circular path. 



The disadvantage of this kind of resistance is well known to cartmen, 

 though of course without consideration of the reason. A horse is said to 

 ])ull better when he is close to his work, that is to say, when he is attached 

 at once to the body to be moved, because every exertion he makes is then 

 communicated at once to the mass : but the leader of a team, unless he 

 keeps the traces constantly on the stretch, may frequently waste a power- 

 ful effort without producing much effect upon the carriage. 



Another inconvenience resulting from harnessing horses in a team, or 

 one before the other, is, that the leader, by tightening the traces, is con- 

 tinually relieving the strain from the body horse, and reciprocally the body 

 horse from the leader ; so that tiiese horses labour under all the disadvan- 

 tages of a long, elastic, and constantly yielding connexion with the load, 

 which is not only fatiguing to them, but, in cases where the resistance is 

 variable, prevents the full and united effect of their exertions being pro- 

 perly communicated to the carriage. For, if a slight oljstacle, as a rut or 

 stone in a road, checks the progress of the vehicle, the shaft-horse can 

 immediately throw his whole weight into the collar, and the united effect 

 of his strength and impetus is conveyed unimpared to the vehiclcj and 

 forces it over the obstacle ; but if any elasticity is interposed between the 

 power and the resistance, as in the case of the traces of the leader of a 

 team, the whole, or the greater part of the effect of impetus is lost, and that 

 force, which, if concentrated in one effort, would effect the object, being 

 lenfrthened into a continued and comparatively feeble pull, is insufficient. 



If we wish to destroy the impetus of a body moving with violence, we 

 receive it with a yielding resistance ; the action of catching a cricket-ball 

 exemplifies this perfectly ; and therefore, if the full effect of momentum is 

 wanted, all elasticity in the direction of the movement should be avoided. 



We have entered rather fully into the consideration of this particular 

 point, because the principle is not only applicable to the mode of commu- 

 nicating the immediate action of the moving power, but will be found also 

 of considerable importance when we arrive at the subjectof wheel-carriages. 



A consideration of these various points brings us to this conclusion, that 

 the draught ought neither to be constantly uniform or without remission, 

 nor yet yielding or elastic: sudden shocks or violent changes in the velo- 

 city must also evidently be disadvantageous, as tending to distress and 

 injure the animal. 



Having determined upon the necessary quality of the resistance, we will 

 proceed to examine into the quantity or the degree of resistance or draught, 

 and the speed best adapted to the exertion of the animal. The useful effect 

 of a horse, or the work done, must evidently depend upon three things, viz: 

 the rate at which he is made to travel, ike power of traction /je can exert) 



