12.

Many have testified to the amount of knowledge which this subject requires, and Hipparchus, in his Strictures on Eratosthenes, well observes, “that no one can become really proficient in geography, either as a private individual or as a professor, without an acquaintance with astronomy, and a knowledge of eclipses. For instance, no one could tell whether Alexandria in Egypt were north or south of Babylon, nor yet the intervening distance, without observing the latitudes.43 Again, the only means we possess of becoming acquainted with the longitudes of different places is afforded by the eclipses of the sun and moon.” Such are the very words of Hipparchus.