

THE PENDULUM. 



125 



being drawn back, one by each hand, into the positions 

 shown in the figure at a and a l respectively, are let go 

 at the same instant. It may be observed that both pen- 

 dulums perform their vibrations in the same time : The 

 time of vibration of a pendulum is not affected by the nature 

 of its substance. This agrees perfectly with the phenomena 

 of freely falling bodies. The leaden bullet has a larger 



FIG. 92 (an. proj. i real size). 



mass than the other and is therefore less easily moved, 

 but the action of gravity upon the leaden bullet is 

 greater in the same proportion as that in which its mass 

 is greater, hence the bullet of lead and that of gypsum 

 move with equal velocities. 



Both pendulums, which for the following experiment 

 may both have leaden bullets, are now brought into the 

 i3ositions a, a 1? fig. 92, and started simultaneously. 



