76 LETTERS ON NATURAL MAGIC. 



of explanation but those which were known to 

 exist at the time of Cellini. If we suppose, how- 

 ever, that the necromancer either had a regular 

 magic lantern, or that he had fitted up his con- 

 cave mirror in a box containing the figures of his 

 devils, and that this box with its lights was carried 

 home with the party, we can easily account for 

 the declaration of the boy, " that as they were 

 going home to their houses in the quarter of 

 Banchi, two of the demons whom we had seen at 

 the amphitheatre went on before us leaping and 

 skipping, sometimes running upon the roofs of the 

 houses, and sometimes upon the ground." 



The introduction of the magic lantern as an 

 optical instrument supplied the magicians of the 

 17th century with one of their most valuable 

 tools. The use of the concave mirror, which 

 does not appear to have been even put up into 

 the form of an instrument, required a separate 

 apartment, or at least that degree of concealment 

 which it was difficult on ordinary occasions to 

 command ; but the magic lantern, containing in a 

 small compass its lamp, its lenses, and its sliding 

 figures, was peculiarly fitted for the itinerant con- 

 juror, who had neither the means of providing a 

 less portable and more extensive apparatus, nor 

 the power of transporting and erecting it. 



The magic lantern shown in the annexed figure 

 consists of a dark lantern, AB, containing a lamp 

 G, and a concave metallic mirror, MN, and it is 

 so constructed that when the lamp is lighted not 

 a ray of light is able to escape from it. Into the 

 side of the lantern is fitted a double tube, CD, 

 the outer half of which D is capable of moving 

 within the other half. A large plano-convex lens 



