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preface.5
Strabo considered that mathematical and astronomical knowledge was indispensable to the science of geography; he says in book i.,Chap. i. § 20 that without some such assistance it would be impossible to be accurately acquainted with the configuration of the earth; and that every one who undertakes to give an accurate description of a place, should describe its astronomical and geometrical relations, and explain its extent, distance, latitude, and climate.Chap. i. § 13. As the size of the earth, he says, has been demonstrated by other writers, we shall take for granted what they have advanced. We shall also assume that the earth is spheroidal, and that bodies have a tendency towards its centre. He likewise says, the convexity of the sea is a further proof that the earth is spheroidal to those who have sailed; for they cannot perceive lights at a distance when placed at the same level as their eyes, but if raised on high, they at once become perceptible.Chap. i. § 20. He also observes, our gnomons are, among other things, evidence of the revolution of the heavenly bodies, and common sense at once shows us that if the depth of the earth were infinite, such a revolution could not take place.Ibid. But Strabo did not consider the exact division of the earth into climates or zones, in the sense in which Hipparchus used the term, and the statement of the latitudes and longitudes of places, which in many instances were pretty well determined in his time, as essential to his geographical description.
