[51] Günther, S. Studien zur Geschichte der mathematischen und physikalischen Geographie. Halle, 1877. Heft 2; Ibn Abî Ja’kûb an-Nadîm. Katâb al-Fihrist (Book of Records), ed. by Gustav Flugel. Leipzig, 1871-1872. 2 vols. The greater part of this Arabic work was written about the year 987 A. D. Edrisi states it as “the opinion of philosophers, of illustrious savants, and of skilled observers in the knowledge of celestial bodies, that the earth is round as a sphere.” See Edrisi, Geography, tr. de l’Arabe en français par P. Amédée Jaubert. (In: Receuel de voyages et de mémoires. Paris, 1830. 2 vols.) Vol. I, p. 1. [52] Zach, F. v. Monatliche Korrespondenz. Gotha, 1806. Vol. XIII, p. 157; Suter, H. Das Mathematiker-Verzeichniss im Fihrist. (In: Zeitschrift für Mathematik und Physik. Leipzig, 1892.) This work contains many references to distinguished oriental scholars who treated in their writings the doctrine of the sphere, the astrolabe, and the armillary sphere. [53] Wittstein, T. Historisch-astronomische Fragmente aus der arabischen Litteratur. (In: Abhandlungen zur Geschichte der Mathematik. Leipzig, 1892. Heft 6, p. 98.) The opinion is here expressed that a terrestrial globe by Edrisi never existed; Hadradauer, C. v. Die Feldzeugmeister Ritter von Hauslabische Kartensammlung. (In: Mitteilungen der K. K. Geographische Gesellschaft zu Wien. Wien, 1886. Neue Folge 19, pp. 387-388.) The opinion is expressed that Edrisi constructed a planisphere and not a globe. Amari, M. Storia dei Musulmani di Sicilia. Firenze, 1868. pp. 453 ff., 669 ff. [54] Dorn, B. Description of an Arabic celestial globe. (In: Transactions of the Royal Asiatic Society. London, 1829. Vol. II, pp. 371-392.) [55] Dorn, op. cit. [56] Dorn, op. cit. [57] See the list as given in the Fihrist, referred to in note 4. Naser ben Mohamed Abul Gioush, King of Castile, is referred to as having been much interested in astronomy, in which science he acquired such proficiency as to enable him to construct a number of very useful astronomical instruments. [58] Lelewel, J. Géographie du moyen âge. Bruxelles, 1857. Vol. I, p. 116; Jourdain. Mémoire sur l’observatoire de Méragah. Paris, 1810. It is well known that under the direction of Nasr-Eddin, who was called to the charge of this observatory by Hulagu Khan, astronomical instruments were constructed. [59] Dorn, op. cit. [60] See the Fihrist, also a list as given by Dorn. [61] Dorn, op. cit. [62] Dorn, op. cit. [63] Meucci, F. Il globo celeste arabico del seculo XI esistente nel Gabinetto degli strumenti antichi di Astronomia, Mathematica nel R. Istituto di Studi Superiori. Firenze, 1878. [64] Assemani, S. Globus coelestis cufico-arabicus Veliterani Musei Borgiani. Patavii, 1790. [65] Dorn, op. cit.