ENERGY AND ITS RELATION TO USE OF MACHINES 555 



quires six or eight men working one day to do a full horse- power- 

 day cf work. Now the cost of a man's daily food varies 

 greatly, but it is probably true that the cost of food for a 

 laboring man is generally somewhere from 30 to 60 cts. a 

 day. The food for a man is not nearly so great in quantity 

 as that consumed by a horse nor does it contain so many cal- 

 ories of heat, but it is of much finer quality, it should be much 

 more varied, and it must be cooked and prepared so that its 

 cost per pound is several times as great. It is probably true 

 that the cost of food for the well-fed workingman is as great 

 as that of the well-fed working horse. Since man can do but 

 about one-seventh as much work as the horse, it is evident 

 that man is an expensive motor when compared with either a 

 horse or a steam engine. 



When thus considering merely the cost of the food of the 

 workingman, we are entirely neglecting the cost of com- 

 fortable shelter, of clothing, of reading matter, of traveling 

 expenses, of amusements, and all the other elements of higher 

 living which make life really worth while. Moreover, the 

 laboring man is usually the head of a family and therefore 

 must provide food, shelter, clothing, school books, and all 

 the other necessities of life for the several members of his 

 family. When we consider all these things, we see clearly 

 that no working man can possibly compete with other forms 

 of motors. He must labor at tasks which other motors are 

 unable to perform. 



COST OF 1 HORSE-POWER-DAY OF WORK, CONSIDERING FUEL AND 



FOOD ONLY 



By steam engine 4 to 5 cts. 



By gasoline engine 10 to 15 cts. 



By horse 30 to 40 cts. 



By man $2 . 50 to $5 . 00 



660. Why We often Use the Horse instead of the Steam 

 Engine. The horse, not only does useful work, but while doing 

 it he is obliged to do a large amount of useless work. The horse 

 in Art. 658, Prob. 2, not only hauled the load 20 miles per 



