88 WELLS'S NATURAL PHILOSOPnT. 



body ; the bones o:N;lie body facilitate and direct the ap^ 

 plication of this force. 



Beasts of prey possess the greatest amount of muscular power ; but somo 

 very small animals possess muscular power in proportion to their bulk, in- 

 comparably greater than the largest of the brute creation. A flea, considered 

 relatively to its size, is stronger than an elephant, or a lion. 



A man can exert his greatest active strength in pulling up- 

 exert his great- ward from his feet, because the strong muscles of the back, 

 ebt strgngth f ^^^ those of the upper and lower extremities, are then brought 

 most advantageously into action. 



The comparative effect produced in the different methods of applying the 

 force of a man, may be indicated as follows : in tho action of turning a crank, 

 or handle, his force maybe represented by the number 17; in working a 

 pump, by 20 ; in pulling downward, as in ringing a bell, by 39 ; and in pull- 

 ing upward from the feet, aa in the action of rowing, by 41. 



What is the 1'7^6. The estimate of the uniform strength 



efre"gth*of « ^^ ^^ Ordinary man, for the performance of or- 



°"'°' dinary daily mechanical labor is, that he can 



raise a weight of 10 pounds to the height of 10 feet once 



in a second, and continue to do so for 10 hours in the 



day. 



r^ . , .u 177. The estimated strength of a horse is, 



What i« the , , f, , 



estimntpd that hc Can raise a weight of 33,000 pounds 



•trength of a ,•,., , n • • oi 



horse, or & to the hcicrht ot one foot m a mmute. feucn 



"horse-power?" ^ n n . -iii ct 



a measure of force is called a horse- 



POWEB." 



The strength of a horso is considered to be equal to that of five men. The 

 average strength which a horse can exert in drawing is about 1600 pounds. 



What is water- 178. Water-power is the power obtained 

 power T y^^ ^^iQ action of water falling perpendicularly, 

 or running down a slope, by the influence of gravity. 

 What is the 179. When work is performed by any agent, 

 fomjarfng the thcrc Is always a certain weight moved over a 

 perfo"4ed''by'' Certain space, or a resistance overcome ; the 

 different forces? amouut of work performed, therefore, will de- 

 pend on the weight, or resistance that is moved, and the 

 space over which it is moved. For comparing different 

 quantities of work, done by any force, it is necessary to 

 have some standard ; and this standard is the power, or 



