The Hexæmeron is the title of nine homilies delivered by St. Basil on the cosmogony of the opening chapters of Genesis.  When and where they were delivered is quite uncertain.  They are Lenten sermons, delivered at both the morning and evening services, and appear to have been listened to by working men.  (Hom. iii. 1.)  Some words in Hom. viii. have confirmed the opinion that they were preached extempore, in accordance with what is believed to have been Basil’s ordinary practice. cf. Rufinus ii. 9.  Internal evidence points in the same direction, for though a marked contrast might be expected between the style of a work intended to be read, like the De Spiritu Sancto, and that of the orations to be spoken in public, the Hexæmeron shews signs of being an unwritten composition.