147. IF the materials for a history of Greek geometry in the second century B. C. are scanty, they become still more so for the next 250 years. Only a few works, and those not of a very valuable character, survive from this period.

About 70 b.c. lived Geminus of Rhodes who seems to have been the freedman of a wealthy Roman and who wrote, beside the astronomical work εἰσαγωγἠ εἰς τὰ ϕαvóμενα, still extant, a book on the Arrangement of Mathematics, περὶ τῆς τῶν μαθη μάτων τάξεως, which, without being expressly historical, con tained abundant notices of the early history of Greek mathematics and from which Proclus and Eutocius derived much of their most correct and valuable information on that subject. A book of this kind, written not long after the classical age by a competent geometer, would, if preserved, have cleared up a hundred difficulties which do not now admit of solution.

148. Probably near to the time of Geminus lived Theodosius (? of Tripolis), who is mentioned by Strabo and Vitruvius and must therefore be a pre-Christian writer, though Suidas attributes to him a commentary on one Theudas of Trajan's time. He is the author of Sphaerica, a very complete treatise on the geometry of the sphere, in three books. It was remarked above, however, on the subject of Euclid's Phaenomena, that both that and the treatise of Theodosius are evidently founded on some earlier work on Spherics, perhaps by Eudoxus. The work of Theodosius contains no trigonometry (a spherical triangle is not mentioned) and there is nothing particularly interesting either in his style or in his discoveries, if indeed he made any.