HUMAN STKENGTH. 



The force of a single man, unaided by machinery, and 

 working to the best advantage, is equivalent to the raising 

 of TO Ibs. 1 foot per second for ten hours in a day. 



The maximum power of a strong man, exerted for 2J min- 

 utes, is equivalent to 18,000 Ibs. raised one foot in a minute. 



A man of ordinary strength exerts a force of 30 Ibs. for 

 10 hours in a day with a velocity of 2^- feet in a second, 

 which is about equal to 4500 Ibs. raised 1 foot in a minute. 



The average weight of men is 150 Ibs. each. 



A man travels, without a load, on level ground, for 8J 

 hours a day, at the rate of 3^ miles an hour, or 31 miles 

 per day. He can carry 111 Ibs. 11 miles in a day. 



A porter going short distances, and returning unloaded, 

 carries 135 Ibs. 7 miles in a day. He can carry, in a wheel- 

 barrow, 150 Ibs. 10 miles a day. 



An average strong man will, for a short period, exert a 

 force with a 



Ibs. 



Drawing knife equal to 100 



An auger, both hands . . . 

 A screw-driver, 1 hand. . 

 A bench-vice, handle. . . . 

 A chisel, vertical pressure 

 A windlass 



Ibs. 

 Pincers, compression equal to 60 



100 I A hand-plane 50 



84 A hand-saw " 36 



72 ! A thumb- vice 45 



72 A brace-bit, revolving " 16 



60 



