Al-Farghānī, Abu’l-‘Abbās Aḥmad Ibn Muḥammad Ibn Kathīr

(b. Farghāna, Transoxania; d. Egypt, after 861)

astronomy.

Al-Farghānī was one of the astronomer-astrologers employed by the Abbasid caliph al-Ma‘mūm, who reigned in Baghdad from 813 to 833. His name sometimes occurs in the Arabic sources as Muḥammad ibn Kathīr, sometimes as Aḥmad ibn Muḥammad ibn Kathīr, and it was probably this variation (in addition to variations of the title of his best-known book—see below) that led Ibn al-Qifū to assume the existence of two Farghānīs, a father and a son. But this assumption has now been generally dismissed as very likely no more than a misunderstanding.¹

A1-Farghānī’s activities extended to engineering, and it is in connection with his efforts as an engineer that we have some biographical information about him. According to Ibn Taghrībirdī, he supervised the construction of the Great Nilometer (al-miqyās alkabīr), also known as the New Nilometer (al-miqyās al-jadīd), also known as the New Nilometer (al-miqyās al–jadīd), at al-Fusṭāṭ (Old Cairo). It was completed in 861, the year in which the caliph al-Mutawakkil, who ordered the construction, died. (The Wafayāt al-a ‘yān of Ibn Khallikān reports the event but, in the Cairo edition, gives the name of the engineer as Aḥmad ibn Muḥammad al-Qarsānī, the last word being no doubt a corruption of “al-Farghānī”—see bibliography.) But engineering was not al-Farghānīs forte, as appears from the following story, which Ibn Abī Uṣaybi‘a transcribed from the Kitāb al-Mukāfaʿa of Aḥmad ibn Yūsuf,² who heard it from Abū Kāmil.

Al-Mutawakkil had charged the two sons of Mūsā ibn Shākir, Muḥammad and Aḥmad, with supervising the digging of a canal named al-Ja‘farī. They delegated the work to “Aḥmad ibn Kathīr al-Farghānī who constructed the New Nilometer,” thus deliberately ignoring a better engineer, Sanad ibn ‘Alī, whom, out of professional jealousy, they had caused to be sent to Baghdad, away from al-Mutawakkil’s court in Sāmarrā. (The caliphal capital had been transferred from Baghdad to Sāmarrā by al-Mu‘taṣim in 836.) The canal was to run through the new city, al-Ja‘fariyya, which al-Mutawakkil had built near sāmarrā on the Tigris and named after himself. Al-Farghānī committed a grave error, making the beginning of the canal deeper than the rest, so that not enough water would run through the length of the canal except when the Tigris was high. News of this angered the caliph, and the two brothers were saved from severe punishment only by the gracious willingness of Sanad ibn ‘Alī to vouch for the correctness of al-Farghānī’s calculations, thus risking his own welfare and possibly his life. As had been correctly predicted by astrologers, however, al-Mutawakkil was murdered, shortly before the error became apparent.³ The explanation given for al-Farghānī’ mistake is that being a theoretician rather than a practical engineer, he never successfully completed a construction (wa-kānat ma‘rifatuhu awfā min tawfīqihi li-annahu mā tamma lahu ‘amalun quaṭṭu). Al-Ya‘qūbī (d. 897) gives a more charitable reason for al-Farghānī’s failure: the stony ground chosen for al-Ja‘fariyya, a place called al-Māḥūza, was simply too hard to dig. He does not mention al-Farghānī by name, but says that work on the canal was entrusted to “Muḥammad ibn Mūsā al-Munajjim and those geometers who associated themselves with him” (Kitāb al-buldān, p. 267).

The Fihrist of Ibn al-Nadīm, written in 987, ascribes only two works to al-Farghānī: (1) “The Book of [the thirty?] Chapters, a summary of the Almagest” (Kitāb al-Fuṣūl, ikhtiyār⁴ al-Majisṭī), and (2) a “Book on the Construction of Sundials” (Kitāb ‘Amal al-rukhāmāt). Ibn al-Quiftī (d. 1248) reproduces the same list under Muḥammad ibn Kathīr (the name that occurs in the Fihrist) but splits the first title into two: Kitāb al-Fusṣūl and Kitāb Ikhtiṣār [sic] al-Majisṭī. To Aḥmad ibn Muḥammad ibn Kathīr he attributes one work, entitled Al-Madkhal ilā ‘ilm hay al-aflāk wa-ḥarakāt al-nujūm (“Introduction to the Science of the Structure of the Spheres and of the Movements of the Stars”) which he describes as consisting of thirty chapters (singular,bāb) presenting a summary (jawāmi‘) of the book by Ptolemy. This is the only title assigned to al-Farghānī by Ibn Ṣā‘id (d. 1244) and Bar-Hebraeus (d. 1286). As has been noted, the two Farghānīs are in fact one; and the same work that Ibn al-Qiftī mistakenly believed to be two has in fact been known by a variety of titles: Jawāmi‘ilm al-nūjūm wa ’l-ḥarkāt al-samāwiyya, Uṣūl ‘ilm al-nūjūm, Kitāb al thalāthīn, Ilal al-aflāk, and so on. This takes us back to the list in Ibn al-Nadīm; but other works must be added to it, notably two(?) treatises on the astrolabe that have come down to us and a commentary on the astronomical tables of al-Khwārizmī.

The Jawāmī‘ or the Elements, as we shall call it here, was al-Farghānī’ best-known and most influential work. He wrote it after the death of al-Ma‘mūn in 833 but before 857. Abu’l-Ṣaqr al-Qabīsī (d967) wrote a commentary on it which is preserved in the Istanbul manuscript, Aya Sofya 4832, fols. 97v–114v. Two Latin translations of the Elements were made in the twelfth century, one by John of Spain (John of Seville) in 1135⁵ and the other by Gerard of Cremona before 1175. Printed editions of the first translation appeared in 1493, 1537, and 1546. (Gerard’s translation was not published until 1910.) Jacob Anatoli made a Hebrew translation of the book that served as a basis for a third Latin version, which appeared in 1590, and Jacob Golius published a new Latin text together with the Arabic original in 1669. (For particulars of these editions, see bibliography.) The influence of the Elements on medieval Europe is clearly attested by the existence of numerous Latin manuscripts in European libraries. References to it in medieval writers are many, and there is no doubt that it was greatly responsible for spreading knowledge of Ptolemaic astronomy, at least until this role was taken over by Sacrobosco’s Sphere. But even then, the Elements of al-Frarghīnī continued to be used, and Sacrobosco’s Sphere was clearly indebted to it. It was from the Elements (in Gerard’s translation) that Dante derived the astronomical knowledge displayed in the Vita nuova and in the Convivio. The following is a summary of the contents of the thirty chapters constituting the Elements

Chapter 1, to which nothing corresponds in the Almagest, describes the years of the Arabs, the Syrians, the Romans, the Persians, and the Egyptians, giving the names of their months and days and the differences between their calendars. Chapters 2–5 expound the basic concepts of Almagest I.2–8: sphericity of the heaven and of the earth, the central position of the earth, and the two primary movements of the heavens. In chapter 5 al-Farghānī gives the Ptolemaic value for the inclination of the ecliptic as 23° 51′, and reports the value determined at the time of al-Ma‘mun as 23° 35′.⁶ (In one of his treatises on the astrolabe he states a different value observed at a later date.) Chapters 6–9 give a description of the inhabited quarter and list the seven climes and the names of well-known lands and cities. In chapter 8 al-Farghānī gives the Ma‘mūnic measurements of the circumference and the diameter of the earth: 20,400 miles and approximately 6,500 miles, respectively. Chapters 10–11 discuss ascensions of the signs of the zodiac in the direct spheres, al-aflāk al-mustaqīma (ie., horizons of the equator), and oblique spheres, al-aflāk al-māāila (i.e., horizons of the climes), and equal and unequal (zamāniyya, temporal) hours

There follow descriptions of the spheres of each of the planets and their distances from the earth (chapter 12); movement of the sun, moon, and fixed stars in longitude (chapter 13); movements of the five planets in longitude (chapter 14); retrograde motions of the wandering planets (chapter 15); magnitudes of eccentricities and of the epicycles (chapter 16); and revolutions of the planets in their orbs (chapter 17). The assertion of chapters 13 and 14 is that the slow eastward motion of the sphere of the fixed stars about the poles of the ecliptic through one degree every 100 years (the Ptolemaic value) is shared by the spheres (the apogees) of the sun, as well as of those of the moon and the five planets.

Chapter 16 concerns movements of the moon and of the planets in latitude; chapter 19, the order of the fixed stars in respect of magnitude and the positions of the most remarkable among them (al-Farghānī counts fifteen); chapter 20, lunar mansions; chapter 21, the distances of the planets from the earth (Ptolemy had stated only the distances of the sun and the moon); chapter 22, the magnitudes of the planets compared with the magnitude of the earth (“Ptolemy only showed the magnitude of the sun and of the moon, but not that of the other planets; it is, however, easy to know the latter by analogy with what he did for the sun and the moon”); chapter 23, rising and setting; chapter 24, ascension, descension, and occultation; chapter 25, phases of the moon; chapter 26, emergence of the five planets; chapter 27, parallax; chapters 28–30, solar and lunar eclipses and their intervals.

Al-Farghānī’s Jawāmi‘ thus gives a comprehensive account of the elements of Ptolemaic astronomy that is entirely descriptive and nonmathematical. These features, together with the admirably clear and well-organized manner of presentation, must have been responsible for the popularity this book enjoyed. It must be noted that, as far as numerical values are concerned, the early printed editions show significant divergences. For example, Mercury’s diameter is given no fewer than four different values: 1/28, 1/20, 1/10, and 1/18 the diameter of the earth. Only one edition (Frankfurt, 1590) has the first correct value.⁷ And in Golius’ 1669 Arabic-Latin edition, which is generally superior to the earlier ones, the value of the same diameter differs in the Latin translation (where it is given as 1/18 the diameter of the earth) from that in the Arabic text (1/28 the diameter of the earth).

Al-Farghānī’s writings on the astrolabe survive in a number of manuscripts bearing different titles: FīṢan‘at al-asṭurlāb, al-Kāmil fi ’l-asṭurlāb, Kitīb ‘Amal al-asṭurlīb. The thirteenth-century manuscript at the British Museum (Or. 5479)⁸ is a substantial work of forty-eight folios (37v-85r) that ought to be counted among the more respectable treatises devoted to this subject in Arabic. Addressed to the scholar who has reached an “intermediate stage in the knowledge of geometry and the computation of the stars” (fol. 38r), it deals at length with the mathematical theory of the astrolabe and purports to correct faulty constructions which were current at the time of its writing. It is no more rule-of-thumb manual and was in fact intended to resolve doubts and difficulties created by such manuals. In this work al-Farghānī states the inclination of the ecliptic to be 23°33′, “as we found by observation in our time” (fol. 46v). On page 49v “our time” is given as the year 225 of Yazdegerd, i.e., a.d. 857–858.

Al-Bīrūnī in his treatise On the Calculation of Chords in Circles assigns to al-Farghānī a work entitled Ilal Zīj al-Khwārizmī, in which, apparently, al-Farghānī gave explanations (‘ilal reasons) for al-Khwārizmī’s computational procedures.⁹ This work has been lost. But in addition to its having been available to and made use of by al-Bīrūnī in the eleventh century, it had been carefully studied by Aḥmad ibn al-Muthannā ibn ‘Abd al-Karīm in the tenth. Ibn al-Muthannā, whose commentary on al-Khwārizmī’s tables survives in Hebrew and Latin translations, tells us that he found al-Farghānī’s book lacking in proofs and altogether suffering from omissions and redundancies. But his remarks would suggest that his own book was either based on al-Farghānī’s treatise or at least took its starting point from it. The Latin translation, made by Hugo of Santalla in the second quarter of the twelfth century, was reported by C. H. Haskins but, following Suter, was wrongly identified as a commentary on al-Farghānī by al-Bīrunī.¹⁰ Two Hebrew versions of Ibn al-Muthannā have recently been published with English translation.¹¹

NOTES

1.See H. Suter’s art. on al-Farghānī in the 1st ed. of the Encyclopaedia of Islam and the rev. art. by J. Vernet in the 2nd ed. See also C. Nallino, “Astrologie e astronomia presso iimusulmani,” in Raccolta di scritti editi e inediti, V (Rome, 1944), 135.

2.Ibn Abī Uṣaybi‘a, Ṭabaqāt al-aṭibbā’, p. 207, refers to Kitāb Husn al-‘uqbā, the title of a ch. in Kitāb al-Mukāfa‘a.

3. According to the same story, going back to Abū Kāmil, another victim of the intrigues of the two sons of Mūsā was the philosopher al-Kindī, whom they had caused to be estranged from al-Mutawakkil and whose library they had confiscated. Sanad’s condition for getting them out of their difficulty was that the library be restored to al-Kindī.

4.Ikhtiyār (selection) is found in G. Flügel’s ed. of the Fihrist and in the (undated) Cairo ed. But the word should no doubt be read ikhtiṣār (summary).

5.See F. Woepcke, “Notice sur quelques manuscrits arabes relatifs aux mathématiques...,” pp. 116–117.

6. Ibn Yūnus reports that the mission ordered by al-Ma‘mūm to prepare the so-called Mumtahan or Ma’mūzīc zīj recorded two values of the obliquity at two different places and times: 23°33′’ at Baghdad in a.h. 214 (a.d. 829–833), and 23°33′52″ at Damascus in a. h. 217 (a.d. 832–833). According to the Princeton University Library MS Yahuda 666 (fol. 37v), al-Farghānī reported two values from the Mumtaḥam: one equal to the Baghdadian determination of 23°33′ and the other the same as that stated in the Elemetns: 23°35′. For Ibn Yūnus, see Notices et extraits des manuscrits de la Bibliotheque Nationale..., VII (Paris, 1803), 56–57.

7.See P. J. Toynbee, “Dante’s Obligations to Alfraganus...,” p. 424, n. 1.

8. Copies of the same work are in the Berlin MSS nos. 5790, 5791, and 5792. A fourth MS at Berlin, no. 5793, fols. lr-97v, not seen by the present writer, seems to be a different work. See W. Ahlwardt, Verzeichnis der arabischen Handschriften der Königlichen Bibliothek zu Berlin, V (Berlin, 1893), 226–227.

9.See “Risāla fi istikhrāj al-watār fi ’‘l-dā‘ira,” in Rasā’il al-Bīrunī, I (Hyderabad, 1949), pp. 128, 168.

10.See C. H. Haskins in Romanic Review, 2 (1911), esp. 7–9, and his Studies in the History of Mediaeval Science, 2nd ed. (Cambridge, Mass, 1927), p. 47, where the same mistaken identification is repeated. But see Millás Vallicrosa, Estudios sobre Azarquiel (Mardrid-Granad, 1943–1950), pp. 25–26.

11. See Bernard R. Goldstein, Ibn al-Muthannā’s Commentary on the Astronomical Tables of al-Khwārizmī (New Haven-London, 1967). Hugo’s Latin text is edited by Eduardo Millás Venderell, S. I., in El comentario de Ibn al-Mutannā‘ a las Tablas Astronómicas de al-Jwārizmī (Madrid-Barcelona, 1963).

BIBLIOGRAPHY

I. Original Works. The Latin trans. of the Elements by John ops Spain was first printed at Ferrara in 1493; Breuis ac perutilis compilatio Alfragani astronomorum pertissimi totum id continens quo ad rudimenta astronomica est opportunum. This was reprinted at Nuremberg in 1537 as part of Continentur in hoc libro Rudimenta astronomica Alfragani. Item Albategnius.... De motu stellarum, ex observationibus tum proprijs, tum Ptolemaei, omnia cum demonstrationibus geometricis &additionibus Ioannis de Regiomonte. Item Oratio introductoria in omnes scientias mathematicas Ioannis de Regiomonte.... Eiusdem introductio in Elementa Euclidis. Item epistola Philippi Melanthonis nuncupatoria, etc. A second reprint, giving the name of the translator for the first time in print, appeared at Paris in 1546; Alfragania astronomorum pertissimi compendium, id omne quod ad Astronomica rudimenta spectat complectens, Ioanne Hispalensi interprete, nunc primum peruetusto exemplari consulto, multis locis castigatus redditum. Francis J. Carmody’s ed., Alfragani Differentie in quibusdam collectis scientie astrorum (Berkeley, Calif., 1943), gives a critical representation of John’s version based on some of the extant MSS.

The Latin by the Heidelberg professor Jacob Christmann, published at Frankfurt in 1590, made use of John’s version as well as of a Hebrew trans. by Jacob Anatoli: Muhamedis Alfragani Arabis Chronologica et astronomica elementa, e Palatinae Bibliothecae verteribus libris versa, expleta, et scholiis expolita. Additus est Commentarius, qui rationem calendarii Romani, Aegyptiaci, Arabici, Persici, Syriaci & Hebraei explicat.... According to Woepcke (see below), p. 120, this version was reprinted in 1618.

Gerard of Cremona’s trans., made before 1175, was not printed until 1910; Alfragano (Al-Fargānī) Il ’Libro dell’ aggregazione delle stelle’ (Dante, Convivio, II, vi–134) secondo il Codice Mediceo-Laurenziano, Pl. 29, Cod. 9 contemporaneo a Dante, introduction and notes by Romeo Campani (Citta de Castello, 1910).

An ed. of the Arabic text was prepared by Jacob Golius on the basis of a Leiden MS. It was published (Amsterdam, 1669) after Golius’ death with a Latin trans. and copious notes covering only the first nine chs. of al-Farghānī’s book: Muhammedis Fil. Ketiri Ferganensis, qui vulgo Alfraganus dicitur, Elementa Astronomica, Arabice & Latine. Cum notis ad res exoticas sive Orientales, quae in iis occurrunt.

Ch. 24 of the Elements, De ortu et occasu Planetarum, et de occultationibus eorum sub radiis solis, was twice printed gother with Sacrobosco’s Sphere: Sphera Ioannis de Sacro Bosco emendata, etc. (Paris, 1556), fols. 53r-54v; (Paris, 1564), fols. 58v-60r.

For the Arabic MSS of al-Farghānī’s works, see C. Brockelmann, Geschichte der arabischen Literatur, I, 2nd ed. (Leiden, 1943), 249–250; supp. vol. I (Leiden, 1936), 392–393. See also H. Suter, Die Mathematicker und Astronomen der Araber und ihre Werke (Leipzig, 1900), pp. 18–19.

MSS of Jacob Anatoli’s Hebrew trans, of the Elements are listed in M. Steinschneider, Die hebraeischen übersetzungen des Mittelalters (repr. Graz, 1956), pp. 554–559 (sec.343).

For Latin MSS of the Elements, see F. Woepcke, “Notice sur quelques manuscrits arabes relatifs aux mathématiques, et récemment acquis par la Bibliothèque impérale”, in Journal asiatique, 5th ser., 19 (1862), 101–127, esp. 114–120; F.J. Carmody, Arabic Astronomical and Astrological Sciences in Latin Translation, A Critical Bibliography (Berkeley-Los Angeles, 1959), pp. 113–116.

A brief but useful description of the early European eds. of the Elements is in P.J. Toynbee, “Dante’s Obligations to Alfraganus in the Vita Nuova and Convivio,” in Romania, 24 (1895), 413–432, esp. 413–417.

II Secondary Literature. Biographical and bibliographical information is in Ibn al-Nadīm, al-Fihrist, G. Flügel, ed., I (Leipzig, 1871), 279; Ibn al-Quifṭī, Ta‘rīkh al-ลukamā’, J. Lippert, ed. (Leipzig, 1930), pp. 78, 286; Ibn Abī Uṣaybi‘a ṣabagīt al-aṭibbāʿ, A. Müller, ed., I (Cairo, 1882), 207–208; Abu ’l-Faraj ibn al-‘Ibrī (BarHebraeus), Tā’rikh mukhtaṣar al-duwal, A. Ṣālhānī, ed. (Beirut, 1890), pp. 236–237; Ibn Ṣā‘id al-Andalusī, Ṭbaqāt al-umam, L. Cheikho, ed. (Beirut, 1912), pp. 54–55; Ibn Khallikān, Wafayāt al-a‘yān I (Cairo, 1882), 483–485—the relevant passage in the ch. on Abu ʿI-Radād is missing from F. Wüstenfeld’s ed. of the Wafayāt, fasc. 4. (Göttingen, 1837), no. 362, p. 53, and from de Slane’s trans., IbnKhallikan’s Biographical Dictionary, II (Paris, 1843), 75; Ibn Taghrībidī, al-Nūjūm al-zārhira, T.G.J. Juynboll and B.E. Mathes, eds., I (Leiden 1851), 742–743; Aḥmad ibn Yūsuf, Kitāb al-Mukāfa’a, Aḥmad Amīn and ’Alī al-Jārim, eds. (Cairo, 1941), pp. 195–198. Gaston Wiet discusses al-Farghānīs construction of the “New Nilometer”, in “Une restauration du Nilomètre de l’ile de Rawda sous Mutawakkil (247/861),’ in Comptes rebdus de l’Académie des inscriptions et belles-lettres (1924), pp. 202–206. Here Wiet cites a reference in Ibn al-Zayāt’s al-Kawākibal-sayāra to the tomb of al-Farghānī in the qarāfa of Cairo, thus giving evidence that al-Ja’farī project is to be found in al-Ya‘qubi, Kitāb al-buldān, in Bibliotheca geographorum arabicorum, M. J. De Goeje, ed., 7 (Leiden, 1892), 266–267. See also Yāqūt, Mu‘jam al-buldān, F. Wüstenfeld ed., II (Leipzig, 1867), 86–87; III (Leipzig, 1868), 17; and IV (Leipzig, 1869), 413.

A trans. of al-Farghānīs intro. to his treatise on the astrolabe (Berlin MS no. 5790) is included in Eilhard Wiedemann “Einleitungen zu arabischen astronomischen Werken”, in Weltall, 20 (1919–1920), 21–26, 131–134; see also Wiedemann’s “Zirkel zur Bestimmung der Gebetszeiten”, in Beiträge zur Geschichte der Naturwissenschaften62, in Sitzungsbeichte der Physikalish-medizinischen Sozietāt in Erlangen, 52 (1922), 122–125. J. B. J. Delambre, in Histoire de l’astronomie du moyen-âge (Paris, 1819), pp. 63–73, gives a detailed account of al-Farghānī’s Elements, chapter by chapter. See also J. L. E. Dreyer, History of the Planetary Systems from Thales to Kepler (Cambridhe, 1906), passim; P. Duhem, Le sustème du monde, II (Paris, 1914), 206–214; and, concerning the relation of Sacrobosco to al-Farghānī, Lynn Thorndike, The Sphere of Sacrobosco and Its Commentators (Chicago, 1949), pp. 15–19. Brief accounts of al-Farghānī are to be found in the Encyclopaedia of Islam and in Sarton’s Introduction to the History of Science, I (Baltimore, 1927), 567.

A. I. Sabra