The experiment with the glass of champagne (page 40) has been employed
by Humboldt, in explanation of the greater audibility of distant
sounds by night than by day. This he attributes to the uniformity of
temperature in the atmosphere by night, when currents of air no longer
rise and disturb its equilibrium; as the air-bubbles in the champagne
interfere with the vibration within the glass. Again, the universal and
dead silence generally prevalent at night, renders our auditory nerves
sensible to sounds which would otherwise escape them, and which are
inaudible among the continual hum of noises which is always going on in
the day time.