44 



ELEMENTS OF SCIENCE 



" the centre of gravity " of the body as being the centre 

 of such parallel and equal forces and is a fixed point 

 which does not change, whatever be the position which 

 the solid body may assume. 



In order that a body should be in equilibrium, it is 

 necessary for it to be supported by a force equal to the 

 body's weight and acting through its centre of gravity in 

 a direction opposite to its weight as in the architectural 

 illustrations just given. 



In a cylindrical body, this centre is in the middle of its 



FIG. 4. 



axis, and if such cylinder be obliquely placed (as in the 

 Leaning Tower of Pisa) it will not fall, provided the weight 

 at the centre of gravity be sustained i.e., if the vertical 

 line from it to the ground comes within its basis of sup- 

 port. If it passes outside this, then such a cylinder, or 

 building, must fall, and this is the reason why a very high 

 pile of dice may so easily be made to topple over; because 

 a very slight inclination will carry the centre of gravity 

 of such a body beyond its base. Bodies, of course, may 



