(S. Paul's),--were collections
of portrait heads of the Popes, which were painted above the colonnade
on the three sides of the nave. In S. Peter's there were two sets, one
on the frieze, above the capitals of the columns, the other on the
walls of the nave, above the cornice; the first is marked with the
letters "G H." in the drawing of Ciampini which is reproduced in
chapter iii., p. 134; the second, with the letters "I L." The set of
the Lateran was painted by order of Nicholas III. (1277-1280). Since
his time the basilica has been burned to the ground twice--in 1308 and
1360--and restored three times. Its last disfigurement, by Innocent X.
and Borromini in 1644, concealed whatever was left standing of the old
building, and made it impossible for us to study its iconic pictures,
if there were any still existing. We possess better information in
regard to S. Peter's, thanks to Grimaldi, who described and copied
both series of medallions before their destruction by Paul V. in 1607.
The lower series, which was painted by order of Nicholas III., began
with Pope Pius I. (142-157) and ended with Anastasius (397-401).
Grimaldi remarks that the Popes of the times of the persecutions, from
Pius to Sylvester, were bareheaded; those of a later age wore the
tiara; all had the round halo, or nimbus, except Tiberius (352-366),
who had a square one. This last particular would prove that the
portraits were originally painted in the time of Tiberius, because the
square nimbus is the symbol of living persons. The upper series above
the cornice was the more important of the two, on account of the
chronological inscriptions which accompanied and explained each
medallion. These inscriptions, which were too small and faint to be
read with the naked eye from below, were not copied before their
destruction. Grimaldi could decipher but a few: SIRICIUS. SEDIT
ANN(_is_) XV. M(_ensibus_) V. D(_iebus_) XX.--FELIX. SEDIT ANN(_o_) I.
M(_ensibus_) ... etc. The heads were bare, and framed by a round halo.
They seem to have been painted at the time of Pope Formosus (891-896),
as were also the fresco-panels which appear in the above-mentioned
drawing of Ciampini.

The guide-books of modern Rome describe the series of S. Paul's,
restored in mosaic after the fire of 1823, as made up of imaginary
likenesses except in the case of later Popes. This statement is not
correct. The original medallions were painted on each side of the
nave, and on the cross o