(), the peripatetic, the astronomer employed by
Julius Caesar to superintend the correction of the calendar (B. C.
46), is called an Egyptian, but may be supposed to have been an Alexandrian Greek. With
the exception of certain allusions to him by name, which simply confirm the fact that he was
considered a skilful astronomer, nothing can be found concerning him. The most definite of
them is that of Simplicius, who says he wrote on astronomy. A sentence of Pliny (Plin. Nat. 2.8) is interpreted by Weidler as implying that
Sosigenes maintained the motion of Mercury round the sun. Riccioli and others represent that
he remained at Rome until the time of Augustus, and aided in the final establishment of the
calendar according to the intention of Julius. But it must be clear that if Sosigenes had
remained at Rome, the Augustan correction never could have been needed : the leap-year would
never have been made a triennial intercalation under the eye of the astronomer himself.
Nevertheless, Pliny (Plin. Nat. 18.25) mentions the Augustan
correction, most probably, as if it had been a correction of the theory of the calendar,
arising out of the further investigations of Sosigenes himself : his words are " ea ipsa ratio
postea comperto errore correcta est, ita ut duodecim annis continuis non intercalaretur ....
et Sosigenes ipse tribus commentationibus, quanquam diligentior esset ceteris,
non cessavit tamen addubitare, ipse semet corrigendo." According to our view of this
passage the tres commentationes are of the three occasions on which,
during the time of Augustus, an intercalation had to be omitted : Pliny seems to make each of
them a separate interference of Sosigenes (whom he may seem to keep alive at Rome for the
purpose) for the correction of his period. And Weidler, in doing honour to the
astronomer for his candour and caution, seems to follow Pliny. (Fabric. Bibl.
Graec. vol. iv. p. 34; Weidler, Histor. Astron. p. 151.)