To follow briefly the history of mosaic as used in the Dark Ages,
the Middle Ages, and the period of the Renaissance, it is interesting
to note that by the fourth century mosaic was the principal decoration
in ecclesiastical buildings. Contantine employed this art very
extensively. Of his period, however, few examples remain. The most
notable is the little church of Sta. Constanza, the vaults of which
are ornamented in this way, with a fine running pattern of vines,
interspersed with figures on a small scale. The Libel Pontificalis
tells how Constantine built the Basilica of St. Agnese at the request
of his daughter, and also a baptistery in the same place, where
Constance was baptized, by Bishop Sylvester.

Among the most interesting early mosaics is the apse of the Church
of St. Pudentiana in Rome. Barbet de Jouy, who has written extensively
on this mosaic, considers it to be an eighth century achievement.
But a later archæologist, M. Rossi, believes it to have been made
in the fourth century, in which theory he is upheld by M. Vitet. The
design is that of a company of saints gathered about the Throne on
which God the Father sits to pass judgment. In certain restorations
and alterations made in 1588 two of these figures were cut away, and
the lower halves of those remaining were also removed, so that the
figures are now only half length. The faces and figures are drawn
in a very striking manner, being realistic and full of graceful
action, very different from the mosaics of a later period, which
were dominated by Byzantine tradition.

In France were many specimens of the mosaics of the fifth century.
But literary descriptions are all that have survived of these works,
which might once have been seen at Nantes, Tours, and Clermont.