POWER OF MEX. Ill 



tally than up a steep, inclined plane. On a level, a horse 

 is as strong as five men, but up a steep hill he is less strong 

 than three; for three men, carrying each 100 pounds, will 

 ascend faster than a horse witli 300 pounds. Hence the 

 obvious waste of po\yer in placing horses on steeply 

 inclined tread-wheels or aprons. The better mode is to 

 allow them to exert their force more nearly horizontally, 

 by being attached to a fixed portion of the machine. For 

 the same reason, the common opinion is erroneous that a 

 horse can draw with less fatigue on an undulating than on 

 a level road, by the alternations of ascent and descent 

 calling difierent muscles into play, and relieving each in 

 turn ; for the same muscles are alike exerted on a level 

 and on an ascent, only in the latter case the fatigue is 

 much greater than the counterbalancing relief. Any per- 

 son may convince himself of the truth on. this subject by 

 first using a loaded wheel-barrow or hand-cart for one day 

 on a level, and for the next up and down a hill; bearing 

 in mind, at the same time, that the human body is better 

 fitted for climbing and descending than that of a horse. 



A draught-horse can draw 1600 pounds 23 miles in a 

 day, on a good common road, the weight of the carriage 

 included. On the best plank-road he will draw more 

 than twice as much. 



A man of ordinary strength exerts a force of 30 pounds 

 for 10 hours a day, with a velocity of 2|- feet per second. 

 He travels, without a load, on level ground, during 8^ 

 hours a day, at the rate of 3.7 miles an hour, 31^ miles a 

 day. He can carry 111 pounds 11 miles a day. He can 

 carry in a wheel-barrow 150 pounds 10 miles a day. 



Well-constructed machines for saving human labor by 

 means of horse-labor, when encumbered with little fric- 

 tion, will be found to do about five times as much work 

 for each horse as where the same work is performed by 

 an equal number of men. For example : an active man 

 will saw twice each stick of a cord of wood in a day. 



