LOCOMOTION AND ITS ORGANS. 321 



or thirty-six thousand feet in a day ; or three millions, six 

 hundred thousand pounds, or four hundred and thirty-two 

 thousand gallons, one foot in a day. The weakest men in 

 health can generally lift about one hundred and twenty-five 

 pounds, and the strongest of ordinary men four hundred 

 pounds. The daily work of a horse is equal to that of five 

 or six men. 



9. There is much difference in the velocity of muscular 

 contraction, as it is regulated entirely by the will. The 

 swiftest race-horse on record was capable of going a mile in 

 a minute ; yet this is trifling compared with the velocity of 

 birds, or even of many small insects, fit has been ascer- 

 tained that a pigeon-hawk can fly one hundred miles in an 

 hour ; the eider-duck ninety miles an hour, and the common 

 crow, twenty-five miles an hour. The swallow flies ninety- 

 two miles an hour, and the swift is said to fly two hundred 

 and fifty miles in the same space of time\ 



10. A falcon belonging to Henry IV. of France, escaped 

 from Fontainbleau, and in twenty-four hours after was in 

 Malta, a distance of one thousand three hundred and fifty 

 miles, making a velocity of fifty-seven miles an hour, sup- 

 posing him to have been on the wing all the time ; but as 

 such birds do not fly by night, his flight was probably at the 

 rate of seventy-five miles per hour. This will give us some 

 idea of the wonderful velocity of the contractions of the 

 muscles of the wings of birds of rapid flight. 



11. But this rapidity of motion is much under the influ- 

 ence of habit. How awkward are the first attempts at 

 writing, drawing, dancing, or playing on musical instru- 

 ments, and with what ease and grace are they performed 

 after a little practice. The same is true with regard to 

 public speaking, or any thing which requires voluntary mo- 

 tion, i 



12. pt is a law of the human system; that relaxation must 

 follow contraction,^-or rest, exercise ; and although the du- 

 ration of action of the voluntary muscles is in a great de- 



