CHAPTER IX,

MATHEMATICAL GEOGRAPHY.

Slow Development of Mathematical Geography—Impulse given to it by
Aristotle, by Subsequent Expeditions, and by the Museum of Alexandria
—Spherical Form of the Earth—Aristotle's Arguments for it—Argument
from Objects seen on the Sea Horizon—Strabo's Statement of it—Measure-
ment of the Earth—Method employed before Eratosthenes—Method of
Eratosthenes—Critidsm of it—Eratosthenes' Measurement of the Habit-
able World—Its Breadth-Its Length-Parallels of Latitude—First
Parallel of Eratosthenes—Other Parallels—The Climata of Hipparchus
cm. 140 B.C.—Meridians of Longitude—Theory of Zones—Aristotle's
View—Virgil's Description—Eratosthenes' Map of the World—Shape of
the Inhabited World—His Sphragides or 'Seals'—His Geographical
Treatise—Its Contents—Its Chief Errors.

THE remarkable development in the study of mathematical
geography which took place during the third
century before Christ was due to the concurrent in-

fluence of several causes. For a considerable time Mathematical
Geography.
after speculation first began to be awakened on
this subject the views which were entertained about it continued
to be very unscientific, and even where one school of thinkers
made advances in the direction of the truth, their opinions were
rejected or ignored by other schools, and still more by the preju-
dices of the vulgar. Questions relating to such topics as the
form of the earth, the division of its surface into zones, and the
existence of an ocean encompassing the habitable world, had been
started, but either had received no satisfactory answer or had
been determined on grounds which would not bear the test of
argument In the course of time astronomical observers, like
Eudoxus of Cnidos (cm. 365 B.C.), contributed the data for
establishing more satisfactory conclusions, .and others in the