VI CONTENTS. 



LETTER VIII. 



Musical and harmonic sounds explained Power of break- 

 ing 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 Produc- 

 tion 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 Page 179 



LETTER IX. 



Singular effects in nature depending on sound Permanent 

 character of speech Influence of great elevations on the 

 character of sounds, and on the powers of speech 

 Power of sound in throwing down buildings Dog killed 

 by sound Sounds greatly changed under particular cir- 

 cumstances Great audibility of sounds during the night 

 explained Sounds deadened in media of different 

 densities Illustrated in the case of a glass of champagne 

 and in that of new-fallen snow Remarkable echoes 

 Reverberations of thunder Subterranean noises Re- 

 markable one at the Solfaterra Echo at the Menai sus- 

 pension bridge Temporary deafness produced in diving- 

 bells Inaudibility of particular sounds to particular ears 

 Vocal powers of the statue of Memnon Sounds in 

 granite rocks Musical mountain of El-Nakous . 212 



LETTER X. 



Mechanical inventions of the ancients few in number 

 Ancient and modern feats of strength Feats of Ecke- 

 berg particularly described General explanation of them 



