ogma merely; all the
enthroned Madonnas, alone or surrounded by significant accessories
or attendant saints; all the Mystical Coronations and Immaculate
Conceptions; all the Holy Families with saints, and those completely
ideal and votive groups, in which the appeal is made to the faith and
piety of the observer. I shall give the characteristic details, in
particular instances, further on.

The altar-pieces in a Roman Catholic church are always either strictly
devotional objects, or it may be, historical subjects (such as the
Nativity) treated in a devotional sense. They are sometimes in several
pieces or compartments. A Diptych is an altar-piece composed of two
divisions or leaves which are united by hinges, and close like a book.
Portable altar-pieces of a small size are generally in this form; and
among the most valuable and curious remains of early religious art are
the Greek and Byzantine Diptychs, sometimes painted, sometimes carved
in ivory[1]. A Triptych is an altar-piece in three parts; the two
outer divisions or wings often closing as shutters over the central
compartment.

[Footnote 1: Among the "Casts from Ancient Ivory Carvings",
published by the Arundel Society, will be found some interesting and
illustrative examples, particularly Class III. Diptych _b_, Class VII
Diptych _c_ and Triptych _f_, Class IX. Triptych _k_.]

On the outside of the shutters or doors the Annunciation was
generally painted, as the mystery which opened the gates of salvation;
occasionally, also, the portraits of the votaries or donors.

Complete examples of devotional representation occur in the complex
and elaborate altar-pieces and windows of stained glass, which often
comprehend a very significant scheme of theology.[1]. I give here
plans of two of these old altar-pieces, which will assist the reader
in elucidating the meaning of others.

[Footnote 1: Still more important examples occur in the porches and
exterior decoration of the old cathedrals, French and English which
have escaped mutilation. These will be found explained at length in
the Fourth Series of Sacred and Legendary Art.]

The first is the altar-piece in the Rinuccini Chapel in the church
of the Santa Croco of Florence. It is necessary to premise that
the chapel was founded in honour of the Virgin and Mary Magdalene;
while the church is dedicated to the Holy Cross, and belongs to the
Franciscans.

[Illustration: Altar-piece]

The compartments are separate