According to an ancient legend, the Emperor Augustus Caesar repaired to the sibyl Tiburtina, to inquire whether he should consent to allow himself to be worshipped with divine honours, which the Senate had decreed to him.  The sibyl, after some days of meditation, took the Emperor apart, and showed him an altar; and above the altar, in the opening heavens, and in a glory of light, he beheld a beautiful Virgin holding an Infant in her arms, and at the same time a voice was heard saying, “This is the altar of the Son of the living God;” whereupon Augustus caused an altar to be erected on the Capitoline Hill, with this inscription, Ara primogeniti Dei; and on the same spot, in later times, was built the church called the Ara-Coeli, well known, with its flight of one hundred and twenty-four marble steps, to all who have visited Rome.

Of the sibyls, generally, in their relation to sacred art, I have already spoken.[1] This particular prophecy of the Tiburtine sibyl to Augustus rests on some very antique traditions, pagan as well as Christian.  It is supposed to have suggested the “Pollio” of Virgil, which suggested the “Messiah” of Pope.  It is mentioned by writers of the third and fourth centuries, and our own divines have not wholly rejected it, for Bishop Taylor mentions the sibyl’s prophecy among “the great and glorious accidents happening about the birth of Jesus.”  (Life of Jesus Christ, sec. 4.)

[Footnote 1:  Introduction.  The personal character and history of the Sibyls will be treated in detail in the fourth series of Sacred and Legendary Art.]

A very rude but curious bas-relief preserved in the church of the Ara-Coeli is perhaps the oldest representation extant.  The Church legend assigns to it a fabulous antiquity; but it must be older than the twelfth century, as it is alluded to by writers of that period.  Here the Emperor Augustus kneels before the Madonna and Child and at his side is the sibyl, Tiburtina, pointing upwards.

Since the revival of art, the incident has been frequently treated.  It was painted by Cavallini, about 1340, on the vault of the choir of the Ara-Coeli.  In the sixteenth and seventeenth centuries, it became a favourite subject.  It admitted of those classical forms, and that mingling of the heathen and the Christian in style and costume, which were calculated to please the churchmen and artists of the time, and the examples are innumerable.

The most celebrated, I believe, is the fresco by Baldassare Peruzzi, in which the figure of the sibyl is certainly very majestic, but the rest of the group utterly vulgar and commonplace. (Siena, Fonte Giusta.) Less famous, but on the whole preferable in point of taste, is the group by Garofalo, in the palace of the Quirinal; and there is another by Titian, in which the scene is laid in a fine landscape after his manner.  Vasari mentions a cartoon of this subject, painted by Rosso for Francis I., “among the best things