66 LETTERS ON NATURAL MAGIC. 



mirrors of a small size, and without the precau- 

 tions necessary to ensure deception, cannot form 

 any idea of the magical effect produced by this 

 class of optical apparitions. When the instru- 

 ments of illusion are themselves concealed,- 

 when all extraneous lights but those which 

 illuminate the real object are excluded, when 

 the mirrors are large and well-polished, and truly 

 formed, the effect of the representation on 

 ignorant minds is altogether overpowering ; while 

 even those who know the deception, and perfectly 

 understand its principles, are not a little surprised 

 at its effects. The inferiority in the effects of a 

 common concave mirror to that of a well-arranged 

 exhibition is greater even than that of a per- 

 spective picture, hanging in an apartment, to the 

 same picture exhibited under all the imposing 

 accompaniments of a dioramic representation. 



It can scarcely be doubted, that a concave 

 mirror was the principal instrument by which 

 the heathen gods were made to appear in the 

 ancient temples. In the imperfect accounts which 

 have reached us of these apparitions, we can trace 

 all the elements of an optical illusion. In the 

 ancient temple of Hercules at Tyre, Pliny men- 

 tions that there was a seat made of a consecrated 

 stone, " from which the gods easily rose." Escu- 

 lapius often exhibited himself to his worshippers 

 in his temple at Tarsus ; and the temple of 

 Enguinum in Sicily was celebrated as the place 

 where the goddesses exhibited themselves to 

 mortals. lamblichus actually informs us, that 

 the ancient magicians caused the gods to appear 

 among the vapours disengaged from fire ; and 

 when the conjuror Maximus terrified his audience 



