230 Mr. C. J. Woodward on a new Form of Wave-apparatus. 



interval elapsing between the successive motions. If, for ex- 

 ample, we have a number of pendulums of equal length hang- 

 ing from a beam, but their lower ends supported so that they 

 are out of the vertical, we shall find on releasing one of them, 

 say the left-hand end one, it will commence swinging to and 

 fro ; by the time the first pendulum has gone over one fourth 

 of its path release the second, and then after equal intervals 

 the third, fourth, &c, and a wave motion will be produced. If 

 each pendulum was drawn aside in a line at right angles to the 

 beam from which they are suspended, a wave corresponding to 

 a ray of polarized light will be produced ; but if each had 

 been drawn aside in the same plane as that of the beam, a 

 wave corresponding to that of a ray of sound would be obtained. 

 We require, then, in order to illustrate these waves, merely a 

 row of pendulums and some arrangement for releasing them 

 in succession. 



The apparatus I have used is represented in the figure. A, A 



Plane wave produced by placing the pendulums in the compartments 

 of the box C and releasing them in succession by lowering the box. In 

 the figure the last ball is about leaving the box. 



