CONTENTS. V 



effects of illumination with light of one simple colour 

 Lamps for producing homogeneous yellow light Methods 

 of increasing the effects of this exhibition Method of 

 reading 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 Page 98 



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 refraction Aerial spectres 

 by reflexion Explanation of the preceding pheno- 

 mena . .127 



LETTER VII. 



Illusions depending on the ear Practised by the ancients 

 Speaking and singing heads of the ancients Exhibi- 

 tion of the Invisible Girl described and explained Illu- 

 sions arising from the difficulty of determining the direction 

 of sounds Singular example of this illusion Nature of 

 ventriloquism Exhibitions of some of the most cele- 

 brated ventriloquists M. St. Gille Louis Brabant M. 

 Alexandre Capt. Lyon's account of Esquimaux ventri- 

 loquists 157 



