Aristotle’s student Theophrastus of Eresus (c. 372–287 B.C.E.) continued his mentor’s study of weather with his On Weather Signs, a book that became the last word on weather. It was consulted all the way through about the twelfth century, when it was still used by scholars of the Byzantine Empire. As a predictor of weather, the book strove to describe how to tell when rain, wind, and storms were coming. Theophrastus’s version of meteorology, though, was still a mix of well-reasoned observation and superstition.