CENTRE OF GRAVITY. 



235 



would move as in fig. 28, so that at each step the weight of the body would 

 be lifted through a considerable height, and therefore the labor of walking 

 would be much increased. 



Fig. 28. 



If a man stand on one leg, the line of direction of his weight must fall within 

 the space on which his foot treads. The smallness of this space, compared 

 with the height of the centre of gravity, accounts for the difficulty of this feat. 



The position of the centre of gravity of the body changes with the posture 

 and position of the limbs. If the arm be extended from one side, the centre 

 of gravity is brought nearer to that side than it was when the arm hung per- 

 pendicularly. When dancers, standing on one leg, extend the other at right 

 angles to it, they must incline the body in the direction opposite to that in 

 which the leg is extended, in order to bring the centre of gravity over the foot 

 which supports them. 



Fig. 29. 



When a porter carries a load, his position must be regulated by the centre 

 of gravity of his body and the load taken together. If he bore the load on his 



Fig. 30. 



