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Art. XV.—Description of an Arabic Quardrant

Published online by Cambridge University Press:  14 March 2011

William H. Morley
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Extract

Considerable attention has been attracted of late years to the astronomical instruments of the people of Asia. Many of these instruments, though far from modern, are remarkable for accuracy and beauty of workmanship, and not a few present admirable specimens of delicate engraving, inlaying, and ornament. The Sedillots, father and son, and others, have done much to elucidate the subject; but it is still far from exhausted, and every addition to our present materials for its illustration cannot fail to be of interest.

Type
Original Communications
Information
Journal of the Royal Asiatic Society , Volume 17 , January 1860 , pp. 322 - 330
Copyright
Copyright © The Royal Asiatic Society 1860

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References

page 322 note 1 See Description of a Elanispheric Astrolabe, constructed for Shah Husain Safawi. King of Persia, and now preserved in the British Museum; comprising an Account of the Astrolabe generally, with Notes'_illustrative and explanatory: to which are added, Concise Notices of Twelve other Astrolabes, Eastern and European, hitherto undescribed. By Morley, William H.. Grand-eagle folio, with 21 Plates. London, 1856Google Scholar. As my work on the Astrolabe is somewhat costly, and a very limited number of copies were printed, I shall transfer into the present paper such portions of it as are necessary for the description of my quadrant, without giving further references to the original work.

page 323 note 1 It appears to me that these last-mentioned numbers are understated each time by ten; they should be from 25° to 90°.

page 323 note 2 The word Kliatt “line,” when used in describing the sphere, signifies the intersection of the plane of any great circle with that of the horizon, or any circle parallel therewith. For example: ‘Abd al-’Ali Barjandi, in his Commentary on the Prolegomena to Ulugh Bgg's Tables, defines the Khatt Nisf an-Nahár, or meridian line, as the section common to the plane of the circle of the meridian and that of the horizon, either rational or sensible.

It must be understood, however, that the word Khatt does not mean the line of intersection as such, but that it is merely an accidental name of a circle of the projected sphere, where the projection of such circle happens to be also the intersection of its plane with the circle of projection. The European anthors used the word line in the same sense.

page 324 note 1 The circle of the midst of the apparent heaven is denned by ‘Abd al-’Ali Barjandi as a great circle passing through the poles of the ecliptic and those of the horizon:

page 326 note 1 Eastern geographers vary very much in tbeir statements of the latitude of Damascus, but the latitude as given on the quadrant is correct.

page 328 note 1 This mosque is sometimes called the Jámi' Bani Umayyah, and is the most remarkable of all the mosques in Damascus, both on account of its vast size and its architecture. Some authors say that it was built by the Emperor Heraclius; by others it has been considered to have been the work of the bishops of that See. It appears to be generally acknowledged that it was formerly the church of St. John of Damascus. It was entirely rebuilt by the Khalifah Walid Ben 'Abd al-Malik in A.H. 90 (A.D. 714), and has since then borne the name of the mosque of the descendants of Umayyah. In the centre of the mosque there is a tomb containing the head of the martyr St. John, son of Zachariah; a relic equally venerated by Christians and Muhammadans. In the account of Damascus translated from the Kitab Manasik al-Hajj by Bianchi, M., and inserted by him in the second volume of the Memoirs of the Geographical Society of Paris, p. 113Google Scholar, et seq., there is a most interesting description and history of the Jami' al-Umawi. The author of the Kitab Manasik al-Hajj states, that when he wrote, in A.H. 1093 (A.D. 1682), there were no less than seventy-five Muazzins attached to this mosque.

page 329 note 1 See, however, M. L. A. Sédillot's remarks in the Mémoires présentés par divers savants à l'acade'mie Royale des Inscriptions, Ire Série, Tome I., pp. 68, 72, 84, 90. It seems possible, from what is there written and quoted, that the are c f is that of the sixth unequal hour; d d that of the obliquity of the ecliptic; and e ethat of the 'Asr.

page 329 note 2 These terms appear to have been used, not only because they indicate the sun's greatest declination, or obliquity of the ecliptic, but also in distinction from the Mail al-Awwal “the first obliquity,” and the Mail ath-Tháni “the second obliquity.” 'Abd al-'Ali Barjandl, in his Commentary on the Prolegomena of Ulugh Beg, defines the Mail al-Awwal as the arc of a circle of declination, comprised between a definite portion or point of the ecliptic and the equinoctial in the nearest direction; the Mail ath-Thani as the arc of a circle of latitude, comprised between the aforesaid point and the equinoctial in the nearest direction; and the Mail al-Kulli as the arc of a circle passing through the four poles (i.e., of the world, and of the zodiac—the solstitial colure) comprised between the ecliptic and the equinoctial in the nearest direction.

The first and second obliquities, when referiible to the same point of the ecliptic, form the two sides of a spherical triangle, having for its base an arc of the equinoctial, and for its apex the given point of the ecliptic: both obliquities have the same maximum, viz., the total obliquity.