Illusions depending on the ear--Practised by the ancients--Speaking
and singing heads of the ancients--Exhibition
of the Invisible Girl described and explained--Illusions
arising from the difficulty of determining the direction
of sounds--Singular example of this illusion--Nature of
ventriloquism--Exhibitions of some of the most celebrated
ventriloquists--M. St. Gille--Louis Brabant--M.
Alexandre--Capt. Lyon’s account of Esquimaux ventriloquists 157
LETTER VIII.
Musical and harmonic sounds explained--Power of breaking
glasses with the voice--Musical sounds from the
vibration of a column of air--and of solid
bodies--Kaleidophone--Singular acoustic figures produced on
sand laid on vibrating plates of glass--and on stretched
membranes--Vibration of flat rulers and cylinders of
glass--Production of silence from two sounds--Production
of darkness from two lights--Explanation of these
singular effects--Acoustic automaton--Droz’s bleating
sheep--Maillardet’s singing-bird--Vaucanson’s flute-player--His
pipe and tabor-player--Baron Kempelen’s
talking-engine--Kratzenstein’s speaking-machine--Mr.
Willis’s researches 179