Hitherto we have principally passed such persons in review, as seem to have been in part at least the victims of their own delusions. But beside these there has always been a numerous class of men, who, with minds perfectly disengaged and free, have applied themselves to concert the means of overreaching the simplicity, or baffling the penetration, of those who were merely spectators, and uninitiated in the mystery of the arts that were practised upon them. Such was no doubt the case with the speaking heads and statues, which were sometimes exhibited in the ancient oracles. Such was the case with certain optical delusions, which were practised on the unsuspecting, and were contrived to produce on them the effect of supernatural revelations. Such is the story of Bel and the Dragon in the book of Apocrypha, where the priests daily placed before the idol twelve measures of flour, and forty sheep, and six vessels of wine, pretending that the idol consumed all these provisions, when in fact they entered the temple by night, by a door under the altar, and removed them. BENVENUTO CELLINI. We have a story minutely related by Benvenuto Cellini in his Life, which it is now known was produced by optical delusion, but which was imposed upon the artist and his companions as altogether supernatural. It occurred a very short time before the death of pope Clement the Seventh in 1534, and is thus detailed. It took place in the Coliseum at Rome. "It came to pass through a variety of odd accidents, that I made acquaintance with a Sicilian priest, who was a man of genius, and well versed in the Greek and Latin languages. Happening one day to have some conversation with him, where the subject turned upon the art of necromancy, I, who had a great desire to know something of the matter, told him, that I had all my life had a curiosity to be acquainted with the mysteries of this art. The priest made answer, that the man must be of a resolute and steady temper, who entered on that study. I replied, that I had fortitude and resolution enough to desire to be initiated in it. The priest subjoined, 'If you think you have the heart to venture, I will give you all the satisfaction you can desire.' Thus we agreed to enter upon a scheme of necromancy.