./. T. Stoddard— Improved Wav< Apparatus, 219 



The apparatus consists of a frame of white wood, holding 

 Borne 270 ebony strips whose tops are trimmed to a sinusoidal 



in (fig. L). ' The strips are 1L""' wide, about 4' thick and 



from 23 to 31 long. They arc Bnpported on a straight edge 



ftrojecting .'»"■"" from the back of the frame. Three Simple w;i 

 Laving a wave-length of 36°° and an amplitude of -1"" are repre- 

 tea, Vertical white lines mark oil' the single wave-lengths, 

 a line is drawn on the strips parallel to the edge on which they 

 it, and the " fundamental" is reproduced in the parallel curve 

 drawn on the front hoard of the apparatus. 



Wave forms cut out of thin hoard can he introduced below 

 the strips (aOy fig. 2). through a slit in tin 4 side of the frame, and 

 raised by a simple arrangement at the hack to a height which 

 is sufficient to lift the strips from their supporting edge. This 



done, the tops of the strips assume the form of the combina- 

 tion curve, while the white line on the strips reproduces the 

 sinusoid on which they rest. As the fundamental is shown on 

 the front board below, one can compare at leisure the compo- 

 nent curves and their resultant. The considerable wave-length 

 and amplitude of the fundamental as well as the thinness of 

 the ebony strips render the combination curves fairly smooth. 

 Since three waves of the fundamental are given, it is possible 

 to produce a complete period of the curve representing the 

 interval of the fourth [3:4], and one or more periods of all 

 intervals expressed by simpler ratios. The effect of difference 

 of phase is readily demonstrated, the straight line representing 

 the "interference" of two elementary tones of the same pitch 

 and intensity being sharply produced. 



Smith College. February, 1890. 



