294 



VII. DYNAMICS OF ROTATING BODIES. 



A pointed steel wire slides easily in the end of the axis of the pen- 

 dulum, and draws a curve upon a plate of smoked glass which is 



Fig. 103 c. Fig. 103d. 



brought against it by a lifting table: By means of a lantern and a 



Fig. 103 e. Fig. 103 f. 



right angled prism the curves are projected upon a wall in the act 



Fig. 103 g! 



Fig. 103 h. 



of being traced. Examples of the curves obtained are shown in 

 Fig. 103. (Figs, g, h, i are hypocycloids drawn geometrically, for 



