Note 357 — Chapter III · THE CONTRIBUTION OF THE MOSLEMS

Ibn Yūnūs, Abū-l-Fidā, and other Moslem geographers tell how, in the time of the Caliph Al-Maʾmūn, geographers were instructed to carry out this measurement on the plain of Sinjār, north of the Euphrates, and also in Syria near Tadmor (Palmyra) and that their results gave 57, 56¼, 56⅔, etc., Arabic miles for a degree. For translation of text of Ibn Yūnūs see Notices et extraits des manuscrits de la Bibl. Natle., vol. vii, Paris, An XII [1803–1804], pp. 94, 96 footnote (2); for Abū-l-Fidā see Reinaud, Géogr. d’Aboulféda, vol. ii, pt. i, 1848, p. 17. See also Miller, Erdmessung, 1919, pp. 30–36, and Schoy, Erdmessungen, 1917, for other figures given by the Moslems and for a recent critical discussion of their measurement. Al-Bīrūnī describes a method of determining an arc of meridian by measuring the curvature of the earth from a mountain of known height. See Schoy, Originalstudien aus “Al-Qânûn al-Masʿûdî,” 1923, pp. 69–74. See also Carra de Vaux, Penseurs de l’Islam, vol ii, 1921, p. 30.