Xll CONTENTS. 



PAG a 



the inscription of coins in the dark Art of deciphering 

 the effaced inscription of coins Explanation of these 

 singular effects Apparent motion of the eyes in portraits 

 Remarkable examples of this Apparent motion of the 

 features of a portrait, when the eyes are made to move 

 Remarkable experiment of breathing light and darkness . 173 



LETTER VI. 



Natural phenomena marked with the marvellous Spectre of 

 the Brocken described Analogous phenomena Aerial 

 spectres seen in Cumberland Fata Morgana in the Straits 

 of Messina Objects below the horizon raised and magnified 

 by refraction Singular example seen at Hastings Dover 

 Castle seen through the hill on which it stands Erect and 

 inverted images of distant ships seen in the air Similar 

 phenomena seen in the Arctic regions- Enchanted coast 

 Mr. Scoresby recognizes his father's ship by its aerial image 

 Images of cows seen in the air Inverted images of horses 

 seen in South America Lateral images produced by re- 

 fraction Aerial spectres by reflection Explanation of 

 the preceding phenomena 198 



LETTER VII. 



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 ventri- 

 loquism Exhibitions of some of the most celebrated ven- 

 triloquists M. St. Gille Louis Brabant M. Alexandre 

 Captain Lyon's account of Esquimaux ventriloquists . 224 



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 vibrat- 

 ing 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 



