Page:Ancient India as described by Ptolemy - John Watson McCrindle.djvu/19

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is its real length.^[1] To this fundamental miscalculation may be referred not a few of the most serious errors to be found in his work. With regard to the question of the length and the breadth of the inhabited part of the earth, a question of first importance in those days, he estimated its length as measured along the parallel of Rhodes^[2] which divided the then known world into two nearly equal portions at 72,000 stadia, and its breadth at 40,000. The meridian in the west from which he calculated his longitudes was that which passed through the Islands of the Blest (Μακάρων Νῆσοι) probably the Canary Islands,^[3] and his most

↑ The Olympic stadium, which was in general use throughout Greece, contained 600 Greek feet, which were equal to 625 Roman feet, or 606¾ English feet. The Roman mile contained 8 stadia, or about half a stadium less than an English mile. A stadium of 600 Greek feet was very nearly the 600th part of a degree, and 10 stadia are therefore just about equal to a Nautical or Geographical mile. According to Eratosthenes, a degree at the Equator was equal to 700 stadia, but according to Poseidônios it was equal to only 500. The truth lay between, but Ptolemy unfortunately followed Poseidônios in his error.
↑ "The equinoctial line was of course perfectly fixed and definite in Ptolemy's mind, as an astronomical line; but he had no means of assigning its position on the Map of the World, except with reference to other parallels, such as the tropic at Syene, or the parallels of Alexandria and Rhodes, which had been determined by direct observation."—Bunbury, Hist. of Anc. Geog., vol. II, p. 560, n. 2.
↑ The Island of Ferro—the westernmost of the Group of the Canaries, which was long taken as the prime meridian, and is still so taken in Germany—is really situated 18° 20′ west of Greenwich, while Capo St. Vincent (called anciently the Sacred Cape) is just about 9°, so that the real difference between the two amounted to 9° 20′ instead of only 2½°. Two corrections must therefore be applied to Ptolemy's longitudes—one-sixth must be deducted because of his under-estimate of the length

[1] The Olympic stadium, which was in general use throughout Greece, contained 600 Greek feet, which were equal to 625 Roman feet, or 606¾ English feet. The Roman mile contained 8 stadia, or about half a stadium less than an English mile. A stadium of 600 Greek feet was very nearly the 600th part of a degree, and 10 stadia are therefore just about equal to a Nautical or Geographical mile. According to Eratosthenes, a degree at the Equator was equal to 700 stadia, but according to Poseidônios it was equal to only 500. The truth lay between, but Ptolemy unfortunately followed Poseidônios in his error.

[2] "The equinoctial line was of course perfectly fixed and definite in Ptolemy's mind, as an astronomical line; but he had no means of assigning its position on the Map of the World, except with reference to other parallels, such as the tropic at Syene, or the parallels of Alexandria and Rhodes, which had been determined by direct observation."—Bunbury, Hist. of Anc. Geog., vol. II, p. 560, n. 2.

[p19-3] The Island of Ferro—the westernmost of the Group of the Canaries, which was long taken as the prime meridian, and is still so taken in Germany—is really situated 18° 20′ west of Greenwich, while Capo St. Vincent (called anciently the Sacred Cape) is just about 9°, so that the real difference between the two amounted to 9° 20′ instead of only 2½°. Two corrections must therefore be applied to Ptolemy's longitudes—one-sixth must be deducted because of his under-estimate of the length

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