LOCOMOTION. 63 



inch from the pivot, on the opposite side ; and a 50 

 pound poise will weigh down a load of 2500 ; for 50 

 times 50=2500. Simple as all this is^ we have many 

 patent balances. 



[From Bigelow's Technology.] 



LOCOMOTION. 



Animals of the more perfect kinds possess the power 

 of shifting their place at will ; which power they exer- 

 cise both in transporting their own bodies, and in con- 

 veying other masses of matter. The chief obstacles 

 which oppose locomotion, or change of place, are 

 gravity and friction ; the last of which is, in most cases, 

 a consequence of the first. Gravity confines all terres- 

 trial bodies against the surface of the earth, with a force 

 proportionate to the quantity of matter which composes 

 them. Before they can be removed from one spot of 

 this surface to another of equal height, they must either 

 be lifted from the ground against the force of gravity, 

 or carried horizontally along the surface, resisting with 

 a degree of friction which increases with their weight. 

 Most kinds of mechanism, both natural and artificial, 

 which assist locomotion, are arrangements for obviating 

 the effects of gravity and friction. 



Motion of Animals. Animals that walk, obviate 

 friction by substituting points of their bodies instead of 

 large surfaces ; and upon these points they turn, as 

 upon centres, for the length of each step, raising them- 

 selves wholly or partly from the ground in successive 

 arcs, instead of drawing themselves along the surface. 

 The line of arcs which the centre of gravity describes 

 is converted into an easy or undulating line, by the 

 compound action of the different joints. As the feet 



