CAEE AND MANAGEMENT OF ANIMALS 775 



and this question can only be answered by saying that it 

 entirely depends upon the pace at which the work is 

 performed. We will take two extreme eases of draught 

 work : the mail-coach horse of sixty years ago, and the 

 plough horse of to-day. One worked for 50 minutes on an 

 8 mile stage, exerting a 40 lb. pull, or 4 per cent, of his 

 body-weight; the other works for 8 or 9 hours a day in 

 a plough, the mean draught being 168 lbs., and the pace 

 IJ miles per hour. In this last case the pull is 11 per 

 cent, of the body-weight (taken at 1,500 lbs.) ; the average 

 amount of daily ploughing is one acre in 9 hours, and this 

 with a nine inch furrow slice gives a distance of 12 miles 

 for the day's work. 



In these two cases one horse works for 50 minutes at 

 rather more than 9J miles an hour, and exerts a force of 

 40 lbs. ; the other does 9 hours work at IJ miles an hour, 

 exerting a force of 168 lbs. The one horse is called upon 

 for a traction effort of -3^ of his body-weight, the other for 

 an effort of -^. 



Although the force exercised in draught is so easily 

 measured, there is a great difficulty in saying at any par- 

 ticular moment what it amounts to ; the fact is that, 

 excepting on a smooth, perfectly level, steel road it is vary- 

 ing every moment, and this is due not only to friction 

 between the road and the wheel, but between the wheel 

 and the axle. The latter friction is due to the weight of 

 the load and is affected by the size of the wheel, so that the 

 larger the wheel the less the friction. 



The friction between the wheel and the road depends 

 upon the nature of the road. The force necessary to move 

 1,000 lbs. in a light four-wheeled cart is :— 



Lbs. 



On a hard dry turnpike road ... ... SOJ^ 



The same road, dirty 

 Hard compact loam 

 Ordinary road 

 New gravelled road 

 Lone sandy road . . . 



This table is very instructive and tells its own tale. 

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39 

 53 



106 

 143 

 204 



