A history of Greek mathematics - Wilbourhall.org

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244 SOME HANDBOOKS
We next have (chap. 31, p. 178) an allusion to the systems
of Eudoxus, Callippus and Aristotle, and a description
(p. 180 sq.) of a system in which the 'carrying' spheres
(called hollow ' '
') have between them solid spheres which by
their own motion will roll (dveXigovcri) the carrying spheres in
the opposite direction, being in contact with them \ These
'
solid ' spheres (which carry the planet fixed at a point on
their surface) act in practically the same way as epicycles.
In connexion with this description Theon (i.e. Adrastus)
speaks (chap. 33, pp. 186-7) of two alternative hypotheses in
which, by comparison with Chalcidius, 1 we recognize (after
eliminating epicycles erroneously imported into both systems)
the hypotheses of Plato and Heraclides respectively. It is
this passage which enables us to conclude for certain that
Heraclides made Venus and Mercury revolve in circles about
the sun, like satellites, while the sun in its turn revolves in
a circle about the earth as centre. Theon (p. 187) gives the
maximum arcs separating Mercury and Venus respectively
from the sun as 20° and 50°, these figures being the same as
those given by Cleomedes.
The last chapters (chaps. 37-40), quoted from Adrastus, deal
with conjunctions, transits, occultations and eclipses. The
book concludes with a considerable extract from DercyHides,
a Platonist with Pythagorean leanings, who wrote (before the
time of Tiberius and perhaps even before Varro) a book on
Plato's philosophy. It is here (p. 198. 14) that we have the
passage so often quoted from Eudemus
'
Eudemus relates in his Astronomy that it was Oenopides
who first discovered the girdling of the zodiac and the revolution
(or cycle) of the Great Year, that Thales was the first to
discover the eclipse of the sun and the fact that the sun's
period with respect to the solstices is not always the same,
that Anaximander discovered that the earth is (suspended) on
high and lies (substituting Keircu for the reading of the manuscripts,
KLveirai, moves) about the centre of the universe, and
that Anaximenes said that the moon has its light from the
sun and (explained) how its eclipses come about' (Anaximenes
is here apparently a mistake for Anaxagoras).
1
Chalcidius, Comm. on Timaens, c. 110. Cf. Aristarchus of Samos,
pp. 256-8.