274 Feeds and Feeding. 



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

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

 meaning tlie work accomplislied in lifting one pound (or one ton) 

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

 "-..T-yijig 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 continuously 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 wiU 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 Hobenkeim experiments ^ the following figures were 

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



Foot-pounda. 



A. Hauling on level track 7,999,800 



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



Perels'' 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. 



» Deutsche Ldw. Prease, 1878, Sept. 18; Ldw. Jahrb. VIII, Suppl. I, 

 p. 116. 



