MECHANICS. 85 



manufacturer naturally inquired, how many horses a 

 steam engine would dispense with ? 



Man Power. 



The strength of an ordinary man walking in hori- 

 zontal direction, and with his body inclining forward, 

 is only equal to twenty-seven pounds, and it is known 

 by experience that a horse can draw horizontally as 

 much as seven men. 



A small animal, or small waggon, is stronger in 

 proportidn to its weight than a large one. 



Dog Power. 



Nine Esquimaux dogs, belonging to Captain Lyon, 

 dragged 1611 pounds, one mile (1760 yards) in nine 

 minutes, and worked in this manner for seven or 

 eight hours a day.* 



Draught. 



In a four-wheeled waggon of the ordinary con- 

 struction, on a good road and horizontal plane, the 

 draught is between ^th and -j^th of the load. If 

 the load, for example, be one ton, the draught will 

 be between 75 and 89 pounds.f 



If a horse, standing still, can by his strength keep 

 a weight of 169 pounds from falling, when suspended 

 over a pulley, he will exert 121 pounds when going 

 two miles an hour, 100 pounds when going three 

 miles an hour, 81 pounds with four miles an hour, 

 64 pounds with five miles an hour, 49 pounds with 

 six miles, 36 pounds with seven miles, 25 pounds 



* It is a curious circumstance in the constitution of these ani- 

 mals, that they have so great a dread of the water as to require a 

 severe beating before they will go into it. In this respect they 

 differ greatly from their neighbours, the Newfoundland dogs. 



t Another and more accurate estimate makes the draught 

 equal to ^th of the load. 



