§ 17. 6. _Ptholome._ The St. John's MS. has _ptolomeys almagest_. '_Almagest_, a name given by the Arabs to the [Greek: megalê syntaxis], or _great collection_, the celebrated work of Ptolemy, the astronomer of Alexandria [floruit A.D. 140-160]. It was translated into Arabic about the year A.D. 827, under the patronage of the Caliph Al Mamun, by the Jew Alhazen ben Joseph, and the Christian Sergius. The word is the Arabic article _al_ prefixed to the Greek _megistus_, "greatest," a name probably derived from the title of the work itself, or, as we may judge from the superlative adjective, partly from the estimation in which it was held.'--English Cyclopædia; Arts and Sciences, i. 223. The Almagest 'was in thirteen books. Ptolemy wrote also four books of judicial astrology. He was an Egyptian astrologist, and flourished under Marcus Antoninus. He is mentioned in the Sompnour's Tale [D 2289], and the Wif of Bathes Prologue, ll. 182, 324.'--Warton, Hist. E. P. ii. 356, ed. 1871. The word _almagest_ occurs in the Milleres Tale, near the beginning (A 3208), and twice in the Wif of Bathes Prologue (D 183, 325). Chaucer says the obliquity of the ecliptic, according to Ptolemy, was 23° 50'. The _exact_ value, according to Ptolemy, was 23° 51' 20"; _Almagest_, lib. i. c. 13. But Chaucer did not care about the odd degree, and gives it nearly enough. See note to ii. 25. 19. 8. _tropos_, a turning; Chaucer gives it the sense of _agaynward_, i.e. in a returning direction. 14. The equinoctial was supposed to revolve, because it was the 'girdle' of the _primum mobile_, and turned with it. See note below to l. 28. 14, 15. 'As I have shewed thee in the solid sphere.' This is interesting, as shewing that Chaucer had already given his son some lessons on the motions of the heavenly bodies, before writing this treatise. 27. _angulus._ We should rather have expected the word _spera_ or _sphera_; cf. 'the sper solide' above, l. 15.