Note 230 — XIX THE CLIMATE OF GREENLAND; THE NORTHERN LIGHTS

Isidore of Seville (d. 636) discusses the five zones in his Etymologiae, iii, c. xliv; xiii, c. vi; and in his De Natura Rerum, c. x. The editors of the Sorö edition suggest that the “other learned men” may be Macrobius and Martianus Capella, the famous encyclopedists of the fifth century (p. 195). But as these writers preceded Isidore by nearly two centuries, it is unlikely that their works were more than indirect sources for the scientific statements in the Speculum Regale. It is more probable that the reference is to such writers as Bede, Rabanus Maurus, and Honorius of Autun, though it is impossible to specify what authority was followed.