(), author of a Greek treatise in two books on the Circular Theory of the Heavenly Bodies (
Of the history of Cleomedes nothing is known, and the date of his work is uncertain. He
professes (ad fin.), that it is compiled from various sources, ancient
and modern, but particularly from Poseidonius (who was contemporary with Cicero); and, as he
mentions no author later than Poseidonius, it is inferred, that he must have lived before, or
at least not much after Ptolemy, of whose works he could hardly have been ignorant if they had
been long extant. It seems, also, from the eagerness with which he defends the Stoical
doctrines against the Epicureans, that the controversy between these two sects was not
obsolete when he wrote. On the other hand, Delambre has shewn that he had nothing more than a
second-hand knowledge of the works of Hipparchus, which seems to lessen the improbability of
his being ignorant of Ptolemy. And Letronne (Journal des Savans, 1821, p.
712) argues, that it is unlikely that Cleomedes should have known anything of refraction
before Ptolemy, who says nothing of it in the
A treatise on Arithametic and another on the Sphere, attributed to a Cleomedes, are said to exist in MS. Vossius (de
Nat. Art. p. 180b.) conject tures that Cleomedes wrote the work on Harmonics attributed
to Cleonides or Euclid. [EUCLEIDES.]
This work is rather an exposition of the system of the universe than of the geometrical principles of astronomy. Indeed, Cleomedes betrays considerable ignorance of geometry (see his account, p. 28, of the position of the ecliptic), and seems not to pretend to accuracy in numerical details.
The first book treats of the universe in general, of the zones, of the motions of the stars and planets, of day and night, and of the magnitude and figure of the earth. Under the last head, Cleomedes maintains the spherical shape of the earth against the Epicureans, and gives the only detailed account extant of the methods by which Eratosthenes and Poseidonius attempted to measure an arc of the meridian.
The second book contains a dissertation on the magnitudes of the sun and moon, in which
the absurd opinions of the Epicureans are again ridiculed; and on the illumination of the
moon, its phases and eclipses. The most interesting points are, the opinion, that the moon's
revolution about its axis is performed in the same time as its synodical revolution about the earth; an allusion to something like almanacs, in
which predicted eclipses were registered; and the suggestion of atmospherical refraction as
a possible explanation of the fact (which Cleomedes however professes not to believe), that
the sun and moon are sometimes seen above the horizon at once during a lunar eclipse. (He
illustrates this by the experiment in which a ring, just out of sight at the bottom of an
empty vessel, is made visible by pouring in water.)
The
Delambre, Hist. de l'Astron. Ancienne, vol. i. chap. 12; Weidler, Hist. Astron. p. 152; Voss. de Nat. Art. p. 117a.;
Fabric. Bibl. Graec. iv. p. 41.