417 



To attain higher velocity, it is necessary still further to reduce the load, and 

 the next Table is calculated upon the supposition of the strain beinp; only 

 one half the last, viz., 62 J lbs ; this is about the average exertion of each 

 horse in a four-horse heavy stage-coach. 



Duration of labour, 



hours per day. Velocity. Effect produced. 



4 . . . . 5J . . . . 613 



3 . . . . 6f . . . . 534 



2 . . . . 74 ... . 434 



1 



II 



307 



In mails or light coaches, where ten, eleven, and even eleven and a half 

 or twelve miles an hour is attained, the average strain of each horse is 

 barely 40 lbs., and the effect produced, or value of work done, not much 

 more than one-half the above. 



It must be remembered, that these tables are all calculated upon the 

 supposition of the road being good, and the work such as not to cause any 

 immediate injury to the animal, and is adapted only to the average quality 

 of horses. They are not therefore at once applicable as data for calcu- 

 lations in all ordinary cases, but only serve to shew the comparative forces 

 which may be exerted under different degrees of speed. The results or 

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

 tance as we have already observed in the cases of slow travelhng, but in 

 rapid travelhng 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 peculiarly 

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

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

 swelling 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 best 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 dis- 

 cussed, and various opinions have been advanced ; some having recom- 

 mended 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, 



2 E 



