274 Feeds and Feeding. 



431. Measuring the work of horses. In measuring work done, 

 the engineer uses as the unit a foot-pound (or foot-ton), the term 

 meaning the work accomplished in lifting one pound (or one ton) 

 one foot high. In comparing the work performed by horses under 

 varying conditions it will be necessary to use the same expres- 

 sion. A nominal horse-power is 33 ; 000 foot-pounds per minute. 

 This amount of work was ascertained by James Watts, the in- 

 ventor of the steam-engine, in a series of experiments with com- 

 pound pulleys. As the capacity of animals for hard work is 

 limited, no horse can work constantly more than eight hours a 

 day. The work done by a horse during a day will be represented 

 by 33, 000 x 8 x 60 = 15, 840, 000 foot-pounds. This is, however, an 

 excessive amount of work. An average horse will do only about 

 22,000 foot-pounds per minute. This work continued for eight 

 hours gives 10,560,000 foot-pounds, which is regarded as an or- 

 dinary day's work for a medium-sized horse. 



In the Hohenheim experiments l the following figures were 

 obtained for eight hours, constituting a day's work: 



Foot-pounds. 



A. Hauling on level track 7,999,800 



B. Working in horse-sweep 12,996,000 



Perels 2 gives the following data for a day's work of eight hours 

 for strong, well-fed horses: 



A. Hauling on level track Foot-pounds. 



Heavy work 17,051,000 



Ordinary work ' 12,996,000 



B. Working in horse-sweep 10,136,900 



432. Wolff's dynamometer. To measure the work performed 

 by the horse in a given time, Wolff constructed a horse dynamom- 

 eter, which may be described as a sweep, the axis of which 

 consisted of two parts a lower stationary cast-iron base and an 

 upper loose cast-iron cover. This cover was connected with the 

 sweep, and could be weighted so that the friction between the re- 

 volving cover and the stationary base on which it rested could be 

 increased at will. The details of the dynamometer, and the ar- 



1 Wolff, Ldw. Jahrb. VIII, Suppl. I, p. 115. 



2 Deutsche Ldw. Presse, 1878, Sept. 18; Ldw. Jahrb. VIII, Suppl. I, 

 p. 115. 



