252 Feeds and Feeding. 



and llagemann, conducted hundreds of tests with horses working on 

 a tread-pcwer so constructed that the distance traveled and the work 

 performed were accurately measured. The animals breather thru 

 a tube inserted in the windpipe, by which means the oxygen in- 

 haled and the carbon dioxid exhaled were accurately determined. 

 (107) To such gaseous intake and outgo was added that which 

 passed thru the skin and vent, as determined by placing the animal 

 in a Pettenkofer respiration apparatus. (61) 



390. Work. — The "foot-pound" and "foot-ton" are terms which 

 denote the work done in lifting a weight of 1 lb. or 1 ton 1 ft. 

 against the force of gravity. When the rate at which the work is 

 done is taken into consideration the unit used is the horse power. 

 A horse power (H. P.) is a power which can lift a weight of 1 lb. 

 at the rate of 33,000 ft. per minute. If by means of rope and pul- 

 leys a horse raises a bucket of water Aveighing 100 lbs. from a well' 

 330 ft. deep in 1 minute, it exerts a force equal to 1 H. P. The 

 pull or draft exerted by the horse may be measured by a dynamom- 

 eter, a crude form of which is a spring balance placed between the 

 singletree or evener and the vehicle or object on which the pull is 

 exerted. According to King,^ the maximum pulling power of a 

 horse when walking on a good road is about one-half its weight, but 

 for steady and continuous work for 10 hours per day and at the 

 rate of 2.5 miles per hour the pull should not be more than one- 

 eighth or one-tenth the weight of the animal. The work performed 

 by horses of different weights would accordingly be as follows: 



Worh performed per day hy horses of various iveiglits. 



The table shows that a 1000-lb. horse will develop 0.67-0.83 H. P., 

 and will do from 6,633 to 8,217 ft.-tons of work when working 10 

 hours per day, heavier horses performing proportionately more 

 work. 



Physics of Agriculture, p. 490. ^ Loc. cit., p. 436. 



