222 THE HORSE IN SERVICE 



attended such efforts. Three thousand foot tons has been fixed 

 by Col. Fred Smith, Veterinary Department, English Army,* as 

 a reasonable daily requirement of the horse, in work. This 

 amounts, in actual performance, to: 



Distance travelled. 



Walking at 3 miles an hour for 8.7 hours 26 miles 



Walking at 4 miles an hour for 5.3 hours 21 miles 



Walking at 5 miles an hour for 3.7 hours 18 miles 



Trotting at 8 miles an hour for 1.5 hours 12 miles 



Cantering at 11 miles an 'hour for 1 11 miles 



The same authority has determined a horse's maximum 

 muscular exertimi to be GS to 78 per cent of his body weight, 

 as registered by his pull on the dynamometer, not on the load. 

 Such a pull, however, could be exerted but a few seconds, as 

 in the starting of a very heavy load. The walking draft of a 

 horse is given by Kingf as about 50 per cent of his body weight, 

 while for a steady, continuous pull a draft of from one-eighth to 

 one-tenth of his own weight is all that can be expected. 



The weight-carrying capacity of a horse as reported by Smith 

 is from one-fifth to one-sixth his weight, at severe exertion. If 

 the pace- is more moderate the weight eavried may be increased. 

 The M'eight carried is expressed in England by stone^ — one stone 

 being fourteen pounds. 



The factors determining the severity of a horse's work are 

 the draft of the load, the pace at which the load is hauled or car- 

 ried, and the duration of the period of work. 



Draft of the Load. — The traction required to move a load 

 is dependent upon the following conditions, acording to King: 



1. The extent to which the pull is opposed by the force of 

 gravity. The increase in the draft required to move a load up 

 hill is proportionate to the increase in the grade. A 10 per cent 

 grade increases the draft 10 per cent of the load. 



2. The resistance offered by the road-bed to the wheel. This 

 is least when the road is smooth and hard ; greatest when rough 

 or yielding. Eough roads impose a series of obstacles over which 



* Veterinary liygiene. 

 t Agricultural Physics. 



