Investigations Concerning the Horse. 287 



due not only to wear of muscles and decomposition of nutritive 

 fluids in the body of the animal, but is partly accounted for by 

 the increased evaporation of water due to the heavier work. The 

 water evaporated daily under varying conditions of exercise, as 

 determined in experiments with different diets, was as follows: 



Water evaporated 

 Condition of horse. per day, Ibs. 



At rest 6.4 



Walking exercise 8.6 



At work, walking 12.7 



Trotting 13.4 



At work, trotting 20.6 



The distance trotted was the same as that walked, and the load 

 drawn was the same. The heat consumed in the evaporation of 

 water was quite considerable. The exhalation of water by breath 

 and perspiration thus diminishes the quantity of food available 

 for the production of work. 



IV. Miscellaneous Findings by the Investigators. 



449. Relation of speed to work. According to M. Fourier, l 

 the daily work of a good horse has a maximum, under the best 

 load for each speed, of about 2.95 feet per second, or 10,596 feet 

 (two miles nearly) an hour. Taking this maximum as unity, 

 he gives the following as the probable value of work per pound 

 at other speeds: 



Feet. Miles. Daily work. 



6,560 1.25 0.69 



10,596 2.00 1.00 



13,120 2.50 .99 



19,680 3.75 .94 



26,240 5.00 .83 



32,800 6.25 .68 



39,360 7.50 .51 



45,920 8.75 .33 



52,480 10.00 .18 



59,040 11.25 .07 



The data presented show that the horse is at his best for draw- 

 ing a load when moving at the rate of about two miles per hour. 



1 Genie Rural, III, 175, quoted by Thurston, The Animal as a Machine 

 and a Prime Motor, p. 52. 



