ount among his personal friends the poet Callimachus,
who had written a treatise on birds, and honourably maintained himself
by keeping a school in Alexandria. The court of that sovereign was,
moreover, adorned by a constellation of seven poets, to which the gay
Alexandrians gave the nickname of the Pleiades. They are said to have
been Lycophron, Theocritus, Callimachus, Aratus, Apollonius Rhodius,
Nicander, and Homer the son of Macro. Among them may be distinguished
Lycophron, whose work, entitled Cassandra, still remains; and
Theocritus, whose exquisite bucolics prove how sweet a poet he was.

[Sidenote: The writings of Apollonius.]

To return to the scientific movement. The school of Euclid was worthily
represented in the time of Euergetes by Apollonius Pergaeus, forty years
later than Archimedes. He excelled both in the mathematical and physical
department. His chief work was a treatise on Conic Sections. It is said
that he was the first to introduce the words ellipse and hyperbola. So
late as the eleventh century his complete works were extant in Arabic.
Modern geometers describe him as handling his subjects with less power
than his great predecessor Archimedes, but nevertheless displaying
extreme precision and beauty in his methods. His fifth book, on Maxima
and Minima, is to be regarded as one of the highest efforts of Greek
geometry. As an example of his physical inquiries may be mentioned his
invention of a clock.

[Sidenote: The writings of Hipparchus.]

[Sidenote: The theory of epicycles and eccentrics.]

Fifty years after Apollonius, B.C. 160-125, we meet with the great
astronomer Hipparchus. He does not appear to have made observations
himself in Alexandria, but he uses those of Aristyllus and Timochares of
that place. Indeed, his great discovery of the precession of the
equinoxes was essentially founded on the discussion of the Alexandrian
observations on Spica Virginis made by Timochares. In pure mathematics
he gave methods for solving all triangles plane and spherical: he also
constructed a table of chords. In astronomy, besides his capital
discovery of the precession of the equinoxes just mentioned, he also
determined the first inequality of the moon, the equation of the centre,
and all but anticipated Ptolemy in the discovery of the evection. To him
also must be attributed the establishment of the theory of epicycles and
eccentrics, a geometrical conception for the purpose of resolving the
apparen