of the Relative Intensities in Sound. 45 
mirror will present its well known serrated appearance. On 
sounding the second body impulses from it will meet those from 
the first body, and if the phases of vibration of the impulses on 
the manometric membrane are opposed and of equal intensity, 
the membrane will remain at rest and the flame will now appear 
in the mirror as a band of light with a rectilinear upper border. 
But although the intensities of the pulses can easily be ren- 
tie equal y altering the distance of one of the resonators 
ing means. I cut a piece out of one of the tubes equal in 
length to a half-wave of the note we are experimenting on, and 
replace this piece of tubing with a glass tube of the same length, 
ito which slides another glass tube also of half a wave in 
length. Now the experimentation becomes expeditious and 
If the latter do not entirely disappear from the band of light in 
the mirror, w 
measured, and the inverse ratio of the — of these 
distances will be the ratio of the intensities of the vibrations at 
