Aristotle (384–322 B.C.), in two of his extant works, the _Meteorologica_ and the treatise on the Heavens, revealed something of his ideas on physical geography and the figure of the earth and its relations to the heavenly bodies. He believed the earth to be a sphere in the centre of the universe, because that was a form which matter gravitating towards a centre would necessarily assume, also because the shadow cast by the earth on the moon during an eclipse is circular. He accepted the conclusion that the circumference of the earth was 400,000 stadia (nearly 46,000 miles). His views with reference to the cosmical relations of the earth were the same as those adopted by Eudoxus of Cnidus (_fl._ middle fourth century), but he did his best to prove them. He adopted, however, the prevalent view that the habitable world was confined to the temperate zone between the tropics and the arctic regions. He believed there must be a temperate zone in the southern hemisphere, though he did not suggest that it must be inhabited. In the _Meteorologica_ he treats of such subjects as weather, rain, hail, earthquakes, etc., and their causes. He recognized that changes took place in the relations of land and sea. His knowledge of the origin and course of rivers and their relation to mountain systems was confused, and mainly erroneous; and it would seem that little progress had been made in geographical knowledge since the time of Herodotus. In the work of Aristotle’s successor, Theophrastus of Lesbos (_c._ 372–287), an important department of geographical study--that of distribution--finds a place in its particular application to plants.