60 



WELLS'S NATURAL PHILOSOPHY. 



the "base of a body, and the nearer its principal mass is to 

 the base, or, in other words, the lower its cen- 

 ter of gravity is, the firmer it will stand. 



A pyramid, for this reason, is the firmest of all structures. 

 The base upon which the human body rests, or is supported, 

 is the two feet and the space included between them. The 

 advantage of turning out the toes when we walk is, that it 

 increases the breadth of the base supportmg the body, and 

 enables us to stand more securely. 

 In every movement of the body, a man adjusts his position unconsciously, 

 in such a way as to support the center of gravity, and cause the line of di- 

 rection to fall within the base. 



Why does a ^ person carrying a load upon his back, bends forward in 



fng'a load up- order to bring the center of gravity and his load over hia 



on his back feet 

 l>end over ? 



When will 

 body stand 

 most firmly ? 



What is the 

 advantage of 

 turning out the 

 toes in walk- 

 ing? 



Fig. 19. 



Fig. 20. 



Why does a 

 'person lean for- 

 ward in ascend- 

 ing a hill, and 

 backward in 

 descending ? 



Why is a high 

 carriage more 

 liable to over- 

 turn than a low 

 one? 



Fig. 21. 



If he carried the load in the position of A, Fig. 19, he would be liable to 

 fall backward, as the direction of the center of gravity would fall beyond his 

 heels ; to bring the center of gravity over his feet, he assumes the position 

 indicated by B, Fig. 20. 



For the same reason, when a 

 man ascends a hill he leans for- 

 ward, and when he descends he 

 leans backward. See Fig. 21. 



A high carriage is much more 

 liable to be overset by an irregu- 

 larity in the road than a low one ; 

 because the center of gra\aty being 

 high, the line of direction is easily 

 thrown without the base. This 

 will appear evident from the following illustration, Fig. 22. 



