Dôsitheus of Pêlousion
Flourished Pêlousion (Tell el-Farama, Egypt), 230 BCE
Dôsitheus was a student of Konon ( Conon ) of Samos and a correspondent of Archimedes of Syracuse. He wrote and observed in Alexandria, and perhaps on the island of Kos, but nothing further is known of his life. The name, meaning “god-given,” is common, but all other prominent Ptolemaic bearers were Jewish, so it may translate as Nathaniel. Pêlousion, at the easternmost mouth of the Nile, was an important coastal border fortress and customs station of Ptolemaic Egypt. During Dôsitheos’s lifetime, Pêlousion was often the point of departure for Ptolemaic attacks on the neighboring Seleukid Kingdom (in the wars of 274–271, 260–253, 246–241, and 221–217 BCE).
After Konon died, Archimedes resorted to Dôsitheus as the addressee of his mature works – On the Quadrature of the Parabola, On the Sphere and Cylinder(two books, separately addressed), On Spirals, and On Conoids and Spheroids. In turn, Dôsitheus solicited proofs from Archimedes, who attributed to him not expertise but only familiarity with geometry. Dôsitheus’s astronomical contributions chiefly concerned the calendar, on which he wrote three works – Appearances of Fixed Stars(rising and setting dates), Weathersigns(seasonal weather predictions based on astronomical phenomena), and On the Eight-year Cycle of Eudoxos(all lost). Notes from the first and second are preserved in the calendar appended to Geminus ’s Introduction, in Pliny and in Ptolemy ’s work of the same name (usually cited as Phaseis). Dôsitheus is also attested to have written a work To Diodoros(an exceedingly common name), apparently giving information on the life of Aratus .
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