CONTENTS. 



LETTEES ON NATUKAL MAGIC. 



LETTER I. 



PAGE 



Extent and interest of the subject Science employed by ancient 

 governments to deceive and enslave their subjects In- 

 fluence of the supernatural upon ignorant minds Means 

 employed by the ancient magicians to establish their 

 authority Derived from a knowledge of the phenomena of 

 Nature From the influence of narcotic drugs upon the 

 victims of their delusion From every branch of science 

 Acoustics Hydrostatics Mechanics Optics M. Sal- 

 verte's work on the occult sciences Object of the follow- 

 ing letters 89 



LETTER II. 



The Eye the most important of our organs Popular descrip- 

 tion of it The eye is the most fertile source of mental 

 illusions Disappearance of objects when their images fall 

 upon the base of the optic nerve Disappearance of objects 

 when seen obliquely Deceptions arising from viewing 

 objects in a faint light Luminous figures created by 

 pressure on the eye either from external causes or from 

 the fulness of the blood-vessels Ocular spectra or acci- 

 dental colours Remarkable effects produced by intense 

 light Influence of the imagination in viewing these 

 spectra Remarkable illusion produced by this affection of 

 the eye Duration of impressions of light on the eye 

 Thaumatrope Improvements upon it suggested Dis- 

 appearance of halves of objects or of one of two persons 

 Insensibility of the eye to particular colours Remarkable 

 optical illusion described ...... 95 



