Sir David Brewster, who quotes Cellini’s narrative in his _Natural Magic_, explains that the demons seen in the Colosseum “were not produced by any influence upon the imaginations of the spectators, but were actual optical phantasms, or the images of pictures or objects produced by one or more concave mirrors or lenses. A fire is lighted and perfumes and incense are burnt, in order to create a ground for the images, and the beholders are rigidly confined within the pale of the magic circle. The concave mirror and the objects presented to it having been so placed that the persons within the circle could not see the aerial image of the objects by the rays directly reflected from the mirror, the work of deception was ready to begin. The attendance of the magician upon his mirror was by no means necessary. He took his place along with the spectators within the magic circle. The images of the devils were all distinctly formed in the air immediately above the fire, but none of them could be seen by those within the circle. “The moment, however, the perfumes were thrown into the fire to produce smoke, the first wreath of smoke that rose through the place of one or more of the images would reflect them to the eyes of the spectators, and they would again disappear if the wreath was not followed by another. More and more images would be rendered visible as new wreaths of smoke arose, and the whole group would appear at once when the smoke was uniformly diffused over the place occupied by the images.” Again, the magician may have been aided by a confederate amid the ruins, who manipulated a magic lantern, or some device of the kind. The magician himself may have been provided with a box fitted up with a concave mirror, the lights and figures of {16} the demons. The assertion of the boy that he saw demons skipping in front of him, etc., would be accounted for by the magic box being carried with them. Says the _Encyclopaedia Britannica_, in speaking of Cellini’s adventure: “The existence of a camera at this latter date (middle of sixteenth century) is a fact, for the instrument is described by Baptista Porta, the Neapolitan philosopher, in the _Magia Naturalis_ (1558). And the doubt how magic lantern effects could have been produced in the fourteenth century, when the lantern itself is alleged to have been invented by Athanasius Kircher in the middle of the seventeenth century, is set at rest by the fact that glass lenses were constructed at the earlier of these dates,—Roger Bacon, in his _Discovery of the Miracles of Art, Nature and Magic_ (about 1260), writing of glass lenses and perspectives so well made as to give good telescopic and microscopic effects, and to be useful to old men and those who have weak eyes.” Chaucer, in the _House of Fame_, Book III, speaks of “appearances such as the subtil tregetours perform at feasts”—images of hunting, falconry and knights jousting, with the persons and objects instantaneously disappearing.