The new law in favour of trinitarian Christianity was enforced with as great strictness against the Arians as against the pagans.  The bishops and priests of that party wrere everywhere turned out of their churches, which were then given up to the Homoousians.  Theodosius summoned a council of one hundred and fifty bishops at Constantinople, to re-enact the Nicene creed; and in the future religious rebellions of the Egyptians they always quoted against the Greeks this council of Constantinople, with that of Nicasa, as the foundation of their faith.  By this religious policy, Theodosius did much to delay the fall of the empire.  He won the friendship of his Egyptian subjects, as well as of their Saracen neighbours, all of whom, as far as they were Christian, held to the Nicene creed.  Egypt became the safest of his provinces; and, when his armies had been recruited with so many barbarians that they could no longer be trusted, these new levies wrere marched into Egypt under the command of Hormisdas, and an equal number of Egyptians were drafted out of the army of Egypt, and led into Thessaly.

When the season came for the overflow of the Nile, in the first summer after the destruction of the temples, the waters happened to rise more slowly than usual; and the Egyptians laid the blame upon the Christian emperor, who had forbidden their sacrificing the usual offerings in honour of the river-god.

[Illustration:  250.jpg MANFALOOT, SHOWING THE HEIGHT OF THE NILE IN SUMMER]

The alarm for the loss of their crops carried more weight in the religious controversy than any arguments that could be brought against pagan sacrifices; and the anger of the people soon threatened a serious rebellion.  Evagrius the prefect, being disturbed for the peace of the country, sent to Constantinople for orders; but the emperor remained firm; he would make no change in the law against paganism, and the fears of the Egyptians and Alexandrians were soon put an end to by a most plenteous overflow.

Since the time of Athanasius, and the overthrow of the Arian party in Alexandria, the learning of that city was wholly in the hands of the pagans, and was chiefly mathematical.  Diophantus of Alexandria is the earliest writer on algebra whose works are now remaining to us, and has given his name to the Diophantine problems.  Pappus wrote a description of the world, and a commentary on Ptolemy’s Almagest, beside a work on geometry, published under the name of his Mathematical Collections.  Theon, a professor in the museum, wrote on the smaller astrolabe—­the instrument then used to measure the star orbits—­and on the rise of the Nile, a subject always of interest to the mathematicians of Egypt, from its importance to the husbandman.  From Theon’s astronomical observations we learn that the Alexandrian astronomers still made use of the old Egyptian movable year of three hundred and sixty-five days only, and without a leap-year.  Paul the Alexandrian astrologer,