FEEDING WORKING ANIMALS 389 



evidently meaning the mechanical labor outside the 

 motion of the body. With the knowledge we now possess 

 it is possible to estimate approximately the actual work 

 performed in a given case. 



It would be a good day's labor if a 1,000-pound horse 

 travels 20 miles over a smooth, level, dirt road hauling 

 a wagon with a load of 2,000 pounds. The draft of the 

 loaded wagon would be not far from 100 pounds. A sim- 

 ple calculation shows that the mere moving of such a load 

 the distance of 1 mUe would be equivalent to 264 foot- 

 tons. The energy expenditure in walking a given distance 

 has been measured by Zuntz, who ascertained the differ- 

 ence in oxygen consumption of a horse when at rest and 

 when traveling at a walk over a level road. According 

 to these measurements, it appears that a 1,000-pound 

 horse in walking 1 mUe at the rate of 2 to 3 miles an 

 hour would expend a total energy of 473 foot-tons, 44.4 

 per cent or 201 foot-tons of which belong to the effort of 

 walking, over and above the energy needed for mere 

 maintenance. In the case assumed, a horse would per- 

 form a total labor, in walking and drawing 20 miles, 

 equivalent to Ufting 9,300 tons through a space of 1 foot. 

 This estimate is presented merely as an approximation 

 of the work done under given conditions. 



483. Influence of conditions on the food expenditure 

 for a unit of work. — ^These figures are, perhaps, less im- 

 portant to the owner of work or driving horses than is 

 a knowledge of the influence of speed upon the labor 

 expended in a unit of time. "According to Marcey, the 

 work accomplished in a given time is propo]:tionate to the 

 square of the velocity. His coefficients were 3.42 for 

 walking or pacing, 16 for trotting, 28.62 for cantering, 

 and 68.39 for a full gallop." This general fact would be 



