s in a large measure induced by the custom of using the old
temples for Christian churches; the form of worship was in part guided
by the form of the building, and even the old traditions were engrafted
on the new religion. Thus the traveller Antonius, after visiting the
remarkable places in the Holy Land, came to Egypt to search for the
chariots of the Egyptians who pursued Moses, petrified into rocks at the
bottom of the Red Sea, and for the footsteps left in the sands by the
infant Jesus while he dwelt in Egypt with his parents. At Memphis he
enquired why one of the doors in the great temple of Phtah, then used
as a church, was always closed, and he was told that it had been rudely
shut against the infant Jesus five hundred years before, and mortal
strength had never since been able to open it.

The records of the empire declared that the first Caesars had kept six
hundred and forty-five thousand men under arms to guard Italy, Africa,
Spain, and Egypt, a number perhaps much larger than the truth; but
Justinian could with difficulty maintain one hundred and fifty thousand
ill-disciplined troops, a force far from large enough to hold even those
provinces that remained to him. During the latter half of his reign
the eastern frontier of this falling empire was sorely harassed by the
Persians under their king Chosroes. They overran Syria, defeated the
army of the empire in a pitched battle, and then took Antioch. By these
defeats the military roads were stopped; Egypt was cut off from the rest
of the empire and could be reached from the capital only by sea. Hence
the emperor was driven to a change in his religious policy. He gave over
the persecution of the Jacobite opinions, and even went so far in one
of his decrees as to call the body of Jesus incorruptible, as he thought
that these were the only means of keeping the allegiance of his subjects
or the friendship of his Arab neighbours, all of whom, as far as they
were Christians, held the Jacobite view of the Nicene creed, and denied
the two natures of Christ.

As the forces of Constantinople were driven back by the victorious
armies of the Persians, the emperors had lost, among other fortresses,
the capital of Arabia Nabataae, that curious rocky fastness that well
deserved the name of Petra, and which had been garrisoned by Romans
from the reign of Trajan till that of Valens. On this loss it became
necessary to fortify a new frontier post on the Egyptian side of the
E