he built the great double temple of Venus
and Roma and his own mausoleum, the present Castel Sant' Angelo. At Athens
he completed the great temple of Olympian Zeus, begun by Pisistratus in
the sixth century B. C., and added a new quarter to the city.

*The choice of a successor.* In 136 A. D., Hadrian fell seriously ill and,
having no children, adopted Lucius Ceionius Commodus under the name of
Lucius Aelius Caesar, and clothed him with the tribunician authority.
Hadrian himself withdrew from Rome to his splendid villa at Tibur.
However, Aelius died at the beginning of 138 A. D., and thereupon the
princeps adopted an elderly senator named Titus Aurelius Antoninus, who in
turn adopted the son of the deceased Aelius and his own nephew, Marcus
Annius Verus. Antoninus received the _imperium_ and tribunician power and
became the partner of Hadrian in the principate. After a long and painful
illness the latter died in July, 138 A. D. His later years were clouded by
ill health which rendered him moody and suspicious, and probably led to
the execution of his brother-in-law and the latter's grandson on a charge
of conspiracy. He had never been popular with the Senate and this step
widened the breach between them. Only the energetic action of his
successor prevented the execration of his memory and secured his
deification.

III. THE ANTONINES, 138-192 A. D.

*Antoninus Pius, 138-161 A. D.* Antoninus, who received the name of Pius
in the first year of his rule, was the personification of ancient Roman
piety, i. e. the dutiful performance of obligations in public and private
life. His mildness and uprightness enabled him to act in perfect harmony
with the senators, and as a concession to them he removed the four
_consulares juridici_ whom Hadrian had appointed in Italy.

*His public policy.* Antoninus adhered to Hadrian's peaceful foreign
policy, but had to wage several border wars and suppress some
insurrections in the provinces. In Britain a line of fortifications was
constructed from the Firth of Forth to the Clyde. Antoninus laid great
emphasis upon an upright administration of justice. At this time, too, the
Roman law was greatly enriched through the introduction of principles of
equity and began to receive at the hands of the jurists the systematic
form by which it was later characterized. In 147 A. D. he conferred the
title of Caesar upon the elder of his adopted sons, Marcus Aurelius, whom
he ha