Gemi'nus（*Gemi=nos). This name comes down to us in the manuscripts of Proclus, with a circumflex on the penultimate syllable. Gerard Vossius believes, nevertheless, that it is the Latin word : Petavius and Fabricius admit the circumflex without other comment than reference to Proclus. Any one is justified in saying either Geminus or Geminus, according to his theory. Of the man belonging to this dubious name we know nothing but that, from a passage in his works relative to the Egyptian annus vagus of 120 years before his own time, it appears that he must have been living in the year B. C. 77. He was a Rhodian, and both Petavius and Vossius suspect that he wrote at Rome; but perhaps on no stronger foundation than his Latin name and his Greek tongue, which make them suppose that he was a libertus. Proclus mentions him (p. 11 of Grynoeus) as distinguishing the mathematical sciences into νοητά and αἴδθητα, in the former of which he places geometry and arithmetic, in the latter mechanics, astronomy, optics, geodesy, canonics, and logic (no doubt a corruption of loyistics, or computation; Barocius has ars supputatrix). Again (p. 31)
WorksProclus mentions him as author of a geometrical work containing an account of spiral, conchoid, and cissoid lines. But Delambre (Astr. Anc. vol. i. p. 211) saw reason to question the skill of Geminus both in arithmetic and geometry.
Εἰσαγωγὴ εἰς τὰ Φαινόμενα, which many wrongly make to be a commentary on the Phaenomena of Aratus. The work on the sphere attributed to Proclus is not much more than an abridgment of some chapters of Geminus. The book of the latter is a descriptive treatise on elementary astronomy, with a great deal of historical allusion. There is a full account of it in Delambre (l.c.). The total rejection of the supposed effects of the risings and settings of the stars, &c. upon the weather is creditable to Geminus.