Theodosius, De diebus et noctibus

Theodosius' De diebus et noctibus was one of several texts of pre-Ptolemaic spherical astronomy. Like many other scientific texts it was translated from Greek into Arabic in the ninth century. Qusta b. Luqa was possibly the translator. In two \books" comprising altogether 33 propositions, it describes the lengths of days and nights according to the various positions of the Sun on the ecliptic with respect to the tropics. In this paper the full text of three propositions (I 1, II 20 and 21) alone is given; of the other propositions only the \enunciations" are here edited. The Arabic text is followed by an English translation with comments.