ON DRAUGHT. 



54] 



effects of this force will always be influenced by the quality of the resist- 

 ance, as we have already observed, in the cases of slow travelling ; but in 

 rapid travelling the power is much more expensive, owing to the great loss 

 which we see "by the tables is sustained by increased velocity ; and it is, 

 therefore, the more important to study well the means of applying the 

 power in question. 



In this rapid travelling, the bad consequences of a uniform and constant 

 strain is still more felt by the horses, and the necessity of occasional relief 

 is still more urgent than at low velocities. It is universally admitted by 

 horse proprietors and postmasters, whose interests make them pecuharly 

 sensible on this point, that a flat piece of road is more destructive of horses 

 than the same length of road Avhere gentle rises and alternate flat and 

 SAvelling ground occur ; and that a long hill is easier surmounted where 

 there are occasional short levels, and even descents, than when the whole 

 is one uniform ascent. 



It only remains for us, before we dismiss the subject of the moving 

 power, to consider the particular mode of applying it, or the manner of 

 harnessing the horses. 



Under this head comes the question of the be t direction of the traces, 

 or, as it has generally but less clearly been called, the angle of inclination 

 of the line of traction. This question appears to have been always 

 considered one of great importance: the point has been frequently 

 discussed, and various opinions have been advanced ; some having re- 

 commended 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 prac- 

 tical 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 vipon the legs ; and AD being 

 constant, AB, and, consequently, 

 AF, increase or diminish accord- 

 ing as the angle ADB is increased 

 or diminished : that is to say, the 

 horizontal pull applied to the car- 

 riage is proportionate to the strain 

 upon the legs ; but they are both 

 dependent upon the angle formed 

 by the traces, increasing or dimi- 

 nishing as the latter are inclined 

 downwards or upwards from the 

 collar ; so that whether the traces 

 be inclined upwards, as fig. 4, or 

 doAvnwards, as fig. 6, or whether 

 they be horizontal as fig. 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 



