HORSE POWER. 137 



A horse will live 25 days without solid food, merely drink- 

 ing water. He will live IT days without either eating or 

 drinking. He will live only 5 days when eating solid food, 

 without drinking. 



He attains his full growth in 5 years, and will live 25. 

 His average life is 16 years. 



Horse-power as applied to the measurement of steam-en- 

 gines and waterfalls was first applied by James Watt, the 

 inventor of the steam-engine. From a series of experiments 

 he ascertained that the average strength of a horse was suf- 

 ficient to raise 33,000 Ibs. one foot per minute,* and this 

 unit has been adopted in this country and in England as a 

 general measure of power. 



A waterfall is thus said to have a horse-power for every 

 33,000 Ibs. of water passing a given point per minute for 

 each foot of the fall. To compute the power of a water- 

 fall is given the following 



RULE. Divide the continued product of the width, the 

 depth, the velocity of the water per minute, the height of 

 the fall, and the weight of a cubic foot of water (62J Ibs.) 

 by 33,000. 



EXAMPLE. The flume of a mill is 10 feet wide, the water 

 is 3 feet deep, the velocity is 100 feet per minute, and the 

 fall 11 feet. What is the horse-power of the fall ? 



OPERATION. (10 x 3 x 100 x 11 x62 .)'-*- 33,000 = 62J- 

 horse-power. 



* This is done by means of compound pulleys. 



