A. M. Mayer— Researches in Acousiics, 83 
between a simple sound and the pendulum, or harmonic, vibra- 
- * The equation of this curve is y=a sin(= +2). The length on the axis of 
one recurring period of the curve is 4; the constant a is the maximum ordinate, or 
amplitude. The form of the curve is not affected by a, but any change in its value 
slides the whole curve along the axis of x. It is interesting to observe that this 
t See Helmholtz on the distinction between a sensation and a perception. 
Tonempfindungen, p. 101. 
