Substituting for y in (i) we obtain 
A fsin {(p—o)t+e} sin {(p+o)t+e} 
2 Day = 
Day Gk 0 pt+@ 
322 Mr McCleland, Dynamical system illustrating Fluorescence. | 
: 
— 2wp + const.) = A sin (pt + €) cos at ...(iv) 
which easily reduces to 
p+ kp + orp =4 c= sin {(p— @)t + €} 
es i = sin [((p+@)t+ | + const. ...(v). 
The disturbance therefore consists of two trains of waves of 
different period, and it can be seen that these do not combine to 
give a single train of the same period as the initial disturbance. 
