THE HUMAN BEAST OF BURDEN. 251 



a forehead strap for the top of the head is employed. Even though these 

 marks may not be hereditary, they can not escape the notice of the crani- 

 ometer. 



It should not be overlooked that this human pack animal 'possesses 

 the greatest versatility. In the case of your train, hundreds of men 

 load the cars, carrying burdens on back and trucks; men manipulate 

 the senseless and purposeless thing looking so proud and capable; men 

 unload the train, and, indeed, put the fiery steed to bed. Not so in 

 primitive culture; the man-beast feeds, waters, and curries himself, 

 gathers and adjusts his own load, changes himself into propeller, track- 

 man, carrier ad libitum, besides adapting himself to a multitude of sub- 

 sidiary occupations not here under consideration. Indeed, the man is 

 engineer, engine, freight-car, truck, wheelbarrow, horse cart, dray, tow- 

 path, mule, etc., all combined. 



The mean effect of the power of a man unaided by a machine, working 

 to the best possible advantage and at a moderate estimation, is the rais- 

 ing of 70 pounds 1 foot high in a second for ten hours in a day. 



Two men working at a windlass at right angles to each other can raise 

 70 pounds more easily than one man can raise 30 pounds. 



Mr. Bevan's results with experiments upon human strength are for a 

 short period : 



Pounds of force. 



With a drawing-knife 100 



With anger, both hands 100 



With screw-driver, one hand 84 



With bench-vise, handle 72 



With chisel, vertical pressure 72 



With windlass 60 



With pincers, compression 60 



With hand-plane 50 



With hand-saw 36 



With thumb-vise 45 



With brace-bit, revolving 16 



Twisting with the thumb and fingers only, and with a small screw-driver 14 



By Mr. Field's experiments in 1838 the maximum power of a strong 

 man exerted for two and one half minutes is 18,000 pounds raised 1 

 foot in a minute. 



A man of ordinary strength exerts a force of 30 pounds for ten hours 

 in a day with a velocity of 2£ feet in a second, equal to 4,500 pounds 

 raised 1 foot in a minute, equal to one-fifth of the work of a horse. 



A foot soldier travels in one minute in common time ninety steps 

 equal 70 yards; in quick time, one hundred steps equal 8Q yards; in 

 double-quick time, one hundred and forty steps equal 109 yards. 



He occupies in the ranks a front of 20 inches and a depth of 13 inches 

 without a knapsack ; the interval between the ranks is 13 inches. 



Average weight of men, 150 pounds each; five men can stand in a 

 space of 1 square yard. 



A man travels without a load on level ground during eight and one- 

 half hours a day at the rate of 3.7 miles an hour or 31 J miles a day. He 



