THE CENTRE OF GRAVITY. 



107 



ie three straight lines drawn from the middle of each 

 le to the opposite corner, as in fig. 75. It is of 

 course sufficient to draw only two of these lines, in 

 order to find the centre of gravity. 



If, in fig. 76, A and B are two positions of a body, 

 suspended at a, and having its centre of gravity at s, 

 the body will not be in equilibrium, because the vertical 

 line through s, the line of gravitation, does not* pass 

 through a. But gravity tends to restore the body to 

 the position of stable equilibrium, and the space which 

 the centre of gravity must describe, until equilibrium is 

 restored, is indicated by dotted lines. In all positions 



FIG. 76. 



gravity tends to turn the body towards the line of 

 gravitation drawn through the point of suspension, as 

 indicated in the figure by arrows. It will be seen from 

 B, how elongated objects, such as long poles, sticks, 

 etc., may be c balanced,' on the tip of the finger, for in- 

 stance. Such bodies are in unstable equilibrium, the 

 slightest disturbance makes them fall over, but the 

 Centre of gravity being a good way above the point of 

 support, the time required for returning to the position 



