1. In both Greek and Latin there are volumes written on astronomy by
different writers. Of these Ptolemy[268] is considered chief among
the Greeks. He also taught rules by which the courses of the stars
may be discovered.[269]
[268] Du Breul has _Ptolemaeus, rex Alexandriae_.
[269] The canons by which Ptolemy calculated the position of the
planets. Isidore makes no further reference to them.