Theon of Smyrna: Book on Astronomy

elsewhere as those from Theon1, and more clearly in two places as those given to us by Theon the mathematician2. From this it is evident that there were not only four, but more observations by that Theon, which were given to Ptolemy either by himself or in his name. We do not know where that Theon observed the stars. Indeed, those observations are of such a nature that Ptolemy could have used them without any correction, even if they were not made under the meridian circle of Alexandria. Therefore, the assertion of Delambre3, that Ptolemy was the successor to Theon in the duty of observing the stars at Alexandria, remains in doubt.

As for what Bullialdus, G. J. Vossius, Weidler, Montucla4, Delambre5, and de Gelder6 have asserted—that the mathematician Theon is the same person as Theon of Smyrna—we wish we could believe it more than we are able. For not only are arguments lacking to confirm this opinion of learned men, but also the Astronomy of Theon of Smyrna, almost entirely drawn from the works of the philosophers Adrastus and Dercyllides, does not in the least suggest a sky-observer. Indeed, it contains an error that is also found in Cleomedes, but which is contrary to the observation of Theon the mathematician cited by Ptolemy: for whereas Theon the mathematician had seen Mercury departing 29 degrees from the Sun7...

1 Mathematical Composition, X, 1, p. 195.
2 Ibid., X, 1, p. 193; and X, 2, p. 196.
3 History of Ancient Astronomy, vol. II, p. 336.
4 Op. cit.
5 Hist. of Anc. Astr., vol. I, p. 317; and vol. II, pp. 336 and 638.
6 In the edition of the first 32 chapters of Theon of Smyrna’s Arithmetic (Leiden, 1827, 8vo), Prefatory Matters, ch. 1, § 1-4.
7 In Ptolemy, Mathematical Composition, IX, 9, vol. II, pp. 176-177 (Halma edition).