LOCOMOTOR SYSTEM 



645 



In the second observation the pace is increased, the load reduced, 

 and the working hours diminished by half. 



Stage-Coach. 



Mail-Coach. 



In the above table a small increase in pace necessitates a reduction 

 in the load and distance travelled, and the duration of the period 

 of work. 



The draught employed in the stage-coach in the example given 

 was 62^ pounds per horse on the level, which in the mail-coach was 

 reduced to 40 pounds per horse. It is manifest that with all increase 

 in velocity something must yield — either the effort must be reduced 

 or the duration of labour, or both. It has been shown by actual 

 experiment what amount of increased effort is required to pull a 

 definite weight (1 ton) on a good road at varying velocities and on 

 different gradients.* In the following table only one gradient is 

 taken for the purpose of illustration : 



This shows the increase in force required, even on a good road, 

 for every increase of velocity, and the extra effort needed where a 

 load has not only to be drawn but lifted through a height, as it is 

 in the case of uphill work. 



The Physiology of Draught. — The horse, with its horizontal spine, 

 was never intended to carry weight ; its muscular power is best 

 exerted in hauling, owing to the size of the base on which the animal 

 stands and the immense weight which can be thrown forward beyond 



* ' A Treatise>n Roads,' Parnell, 1838. 



