Sometimes the Annunciation—­still as a mystical subject—­forms an altar-piece of itself.  In many Roman Catholic churches there is a chapel or an altar dedicated expressly to the mystery of the Annunciation, the subject forming of course the principal decoration.  At Florence there is a church—­one of the most splendid and interesting of its many beautiful edifices—­dedicated to the Annunciation, or rather to the Virgin in her especial character and dignity, as the Instrument of the Incarnation, and thence styled the church della Santissima Nunziata.  The fine mosaic of the Annunciation by Ghirlandajo is placed over the principal entrance.  Of this church, and of the order of the Servi, to whom it belongs, I have already spoken at length.  Here, in the first chapel on the left, as we enter, is to be found the miraculous picture of the Annunciation, formerly held in such veneration, not merely by all Florence, but all Christendom:—­found, but not seen—­for it is still concealed from profane eyes, and exhibited to the devout only on great occasions.  The name of the painter is disputed; but, according to tradition, it is the work of a certain Bartolomeo; who, while he sat meditating on the various excellences and perfections of our Lady, and most especially on her divine beauty, and thinking, with humility, how inadequate were his own powers to represent her worthily, fell asleep; and on awaking, found the head of the Virgin had been wondrously completed, either by the hand of an angel, or by that of St. Luke, who had descended from heaven on purpose.  Though this curious relic has been frequently restored, no one has presumed to touch the features of the Virgin, which are, I am told—­for I have never been blessed with a sight of the original picture—­marvellously sweet and beautiful.  It is concealed by a veil, on which is painted a fine head of the Redeemer, by Andrea del Sarto; and forty-two lamps of silver burn continually round it.  There is a copy in the Pitti Palace, by Carlo Dolce.

It is evident that the Annunciation, as a mystery, admits of a style of treatment which would not be allowable in the representation of an event.  In the former case, the artist is emancipated from all considerations of locality or circumstance.  Whether the background be of gold, or of blue, or star-bespangled sky,—­a mere curtain, or a temple of gorgeous architecture; whether the accessories be the most simple or the most elaborate, the most real or the most ideal; all this is of little moment, and might be left to the imagination of the artist, or might be modified according to the conditions imposed by the purpose of the representation and the material employed, so long as the chief object is fulfilled—­the significant expression of an abstract dogma, appealing to the faith, not to the senses or the understanding, of the observer.