Deep-Sea Research, 1967, Vol. 14, pp. 459 to 463. Pergamon Press Ltd. Printed in Great Britain.

Concepts of currents, tides and winds among medieval Arab geographers in the Indian Ocean

A. A. ALEEM*

(Received 22 February 1966)

Abstract--Further medieval Arabic documents are referred to on the history of knowledge of seasonally reversing surface currents, semidiurnal tides and winds in the North lndian Ocean and also in the South Indian Ocean. A "theory" of tides based on the lunar cycle was described by Im~ KHORDAZa~H (846) and by AL MOKADDASI (985). Utilization of tidal currents in turning water- wheels and flour mills in Basra (Irak) in the 10th century was also noted by the second author.

IN HIS interesting article, WARREN (1966) traced our knowledge of the seasonally reversing currents in the North Indian Ocean to the second half of the 9th century or the first half of the 10th century. Warren mainly considered the accounts of AL MASSOUDI (947) and AL EDRISl (1154) and wondered whether earlier reports existed. This paper is intended to throw more light on the history of knowledge of currents, tides and winds in the Indian Ocean, and is based chiefly on Arabic texts written between the 9th and 15th centuries.

It seems almost certain that the reversing currents in the North Indian Ocean, which set in the directions of the summer or winter monsoons, were known to the Arabs at least a century before the time of A1 Massoudi, i.e. f rom the beginning of the 9th century. These currents were mentioned in Kitab al Masalik wal Mamalek (" Book of routes and kingdoms ") written in about 846 A.D. by the famous geo- grapher IBN KHORDAZBEH and published by the Dutch orientalist DE GOEJE in 1889 based on the manuscript in Paris. Thus on page 70 of the Arabic text, he stated :

" T h e Ashtyams (pilots) of the Sea were questioned on flux and reflux; they answered that in the Sea of Faris (Persian Gulf) it follows the rise of the moon; while in the Great Sea (Indian Ocean) it occurs only twice a year. In one period the Sea flows during the summer months to the northeast for six months. Thus a flux occurs in the east of the Sea i.e. in China and a reflux in the west of the Sea. In the other period, the Sea flows during the winter months to the southwest for six months. Thus a flux occurs in the west of the Sea and a reflux in China."

This is an accurate description of reversing currents in the North Indian Ocean based directly on the experience of Arab and Persian pilots. Although IBN KHORDAZBEH'S account seems to be the first available record, we know that Arab and Persian ships frequented the coasts of India, Malaya and China well before the year 846 A.D. Trade with those countries flourished during the 8th century, and already in the year 758 A.D. there was a strong Moslem community of Arabs and Persians in Canton (LEWICKI, 1936). Hence, it seems likely that these currents have been known since that time.

*Oceanography Dept., Faculty of Science, University of Alexandria, Egypt (U.A.R.).

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460 A.A. A t ~

It also appears that AL MASSOUDI (947), AL EDRISI (1154) and several others relied upon IBN KHORDAZB~H when discussing such currents. The latter also reported (p. 69) that " e a c h of the harbours of China is situated on an estuary of a large river into which ships enter, and flow and ebb occur."

It is to be noted that in Arabic there is no one word for " t i d e " but there are words for " f lux" and "ref lux " or " f low " and " e b b . " The word Madd (flux) was often used to describe currents until the 16th century. Thus in the nautical instructions of IsN MxGIo* (15th century) and AL MAHlU (16th century), Madd was used both for " t i d e " and "cur ren t . "

There are two other Arab scholars of the 9th century who also discussed tides, but they were more linguists than geographers. The first was A1-Djahiz (died 869), who also wrote a book on zoology, and the second was Ahmad ibn el Tayeb as Sarkhasi (died 899). The latter, a pupil of the philosopher A1 Kindi, wrote an essay on Seas, Waters and Mountains. Although this work and A1 Djahez's geography were lost, yet they have frequently been quoted by such subsequent scholars as IBN AL FAKIH (902), AL MASSOUDI (947) and others.

IBN AL FAKIH, also known as A1 Hamadani, wrote a geography entitled Kitab al Buldan (" book of countries ") which contains a discussion of the tides (published by DE GOEJE, 1885). Semi-diurnal tides in the South China Sea are referred to by IBN AL FAKIH t (Arabic text, p. 13) while describing the maritime route to China : " A n d from Sunder-Folat (Malaya) to China the ships sail for one month, during which time they pass by mountains for seven days. Once you pass these you arrive at a place called Khanfu (Canton) where there is fresh water (estuary of river). In this place there is flux and reflux twice in the day and night."

IBN AL FAKIH included some ideas as to the causes of tides such as the story of the angel who dips his finger in the China Sea, so the Sea rises and then ebbs upon lifting it, or that of the whale that " inhales water causing ebb and exhales it causing flow." IBN AL FAKIH referred such ideas to theologians such as Ibn Abbas and Kaabal Ahbar. Such legends, however, seem to have arisen in early medieval Arabic folklore from sea stories of sailors. They also appealed to AL MASSOUDI (947), AL EDRISI (1154), and others who included them in their cosmographic works and Mirabilia which had an outstanding public popularity.

Towards the end of the 10th century, an Arab explorer and author named AL MOKADDASI (985) wrote a geography book entitled Ahsan al Takaseem (" The best divisions in recognizing the regions ") (cf. also DE GOFJE, 1906) and included a chapter on " Seas and Rivers," in which he discussed tides, stressing the tidal cycle as follows (p. 12-13) : " A n d this Chinese Sea [Persian Gulf] has fluxes in the middle of the month (lunar month) and towards its beginnings and ends (fortnightly cycle) and twice in the day and night. Of this is the ebb and flow of Basra; the flow pushes the Dagla (river) water thus reversing its direction and filling up the tributaries and irrigating the fields. During the ebb (time) the water is low." AL MOKADDASl also discussed the causes of tides, following IBN AL FAKIH. However, he questioned the stories of the "ange l " and the "breathing of wha le" adding that " w e have

*Manuscripts of these authors were published for the first time by FERRAND (1921--3) and later commented on by ALEEM (1966).

tIncidentally IBN AL FAKm quotes "Solayman the Merchant" (851) (cf. FERRAND, 1922) by name. Hence Solayman is a real personality and his narrative is authentic. Several orientalists have questioned the identity of the author of the manuscript describing this voyage written in 851 A.D.

Concepts of currents, tides and winds among medieval Arab geographers in the Indian Ocean 461

another view on this matter to be mentioned when we discuss the country of Irak." Thus, on pages 124-125 : of the same book " Ebb and flow are both a wonder

and a blessing to the people of A1 Basra. Water visits them in each day and twice at night. (High water is actually meant). It enters rivers, thus irrigating the gardens, and carrying the boats to the villages. When the water ebbs it is also utilized in turning flour mills situated at the entrance of rivers by the receding stream. The flux reaches the boundaries of swamps and its time turns with the cycle of the moon."

Apart from this " l u n a r t h e o r y " of tides, the account on the utilization of tidal stream in turning mills is historically interesting. This idea may have been practiced by the people of A1 Basra well before the 10th century. In the 13th century an Arab scholar of Damascus, Shams ed Din Abou Abdallah Mohammad known as AL DIMISKI (ad Dimichqui), who was an Imam (sheikh) of a little village wrote a remarkable Mirabilia called Nukbet ad Dahr fi Agayeb al Barr wal Bahr (" On the wonders of land and sea "). Finished in about 1325 A.o. the Arabic text was published by MEHREN in 1923, from a copy in St. Petersburg. There is a detailed description of the semi-diurnal tides at Shatt el Arab (Northern Persian Gulf). Most incredible is the exact timing of the tides, so that the time of ebb and flow could easily be predicted. Thus, " A n d all these rivers flow and ebb twice in each day and night. When the sea flows, water rushes into Shatt al Arab to the north, its level rises thus filling up tribu- taries and water-wheels. Those who wish to irrigate their fields and gardens open (gates) and do so, then close them up. The rising water continues during 6 hr then the flow pauses for a while and begins to ebb, running south as it was at the beginning. The water level decreases and tributaries become low; so is the case in water-wheels. This continues for more than 6 hr, because the period of ebb is longer than the period of flow. Again there is a pause and the next high water starts and so on. The timing of flow and ebb turns with days and nights; so that in each day, high water lags behind for 1 hr or rather slightly less; so is the ebb time" (pp. 97-98).

Spring tides were also known to the medieval Arabs. Thus Abul-Feda, a contem- porary of Marco Polo, referred to these in his geography book entitled Takweem al Buldan written in 1321 A.D. (published by REINAUO and DE SLANE in 1840). In this book spring tides (flood Madd in Arabic) are said to occur between the nights of 13-16 of the Arabic (lunar) month (p. 27) and the tidal amplitude in the Eastern Sea and in the Sea of Faris reaches 10 Zira (--~ 5 m) (p. 23).

Medieval Arabs associated surface currents in the Indian Ocean with winds, and tides with the lunar cycle. However, Arabic knowledge of the monsoons preceded knowledge of the reversing currents by some centuries and dates back to pre-Islamic times. In fact those earlier Arabs associated winds with stars and lunar positions in predicting time for travel, agriculture, etc. Indeed, descriptions are to be found in pre-Islamic Arabic poetry to which Alberuni devoted a long chapter in his " Chronology" written in about 1000 A.D. (cf. SACHAU, 1923). Again, Arabic books on winds written by astronomers, popular in the 9th and 10th centuries, called the dominant eastern winds Saba and the western Dabour. These winds were associated with the rise and set of stars. Gab (polaris), Suhayl (southern polar star), rise of Altair and set of Altair marked the four cardinal points. Hence the division of the Arab wind-rose dates back to pre-Islamic times.

Medieval Arabic pilots in the Indian Ocean had sailing directions based upon seasons of the winds, rise and set of stars as well as on other signs; they also used

462 A.A. ALEEM

charts, apparently beginning in the 9th or 10th century. Unfortunately such earlier nautical instructions did not survive, although reference to them is made by AL MOKADDASI (985, p. 10) :

" Be it known that we in Islam have not seen except two seas (oceans). One of them extends between the far east, i.e. China, and Sudan (Africa) turning around the Arabian Island. It has many bays and extensions. People are divided as to its descrip- tion; so are cartographers in drawing it, etc. I have seen charts of this Sea on paper in the library of the Prince of Khurasan, on a (globe ?) possessed by Abil Kasim ibn al Anmati in N a y s a b u r . . . etc.

As for me I have sailed in this sea (Indian Ocean) for about 2000 Farsak ( : ,~ 6000 km), and circumnavigated all Arabia from Kolzum (Suez) to Abbadan, apart from drifting on islands and in high seas. I befriended sheikhs (masters) in this sea who were born and raised in pilot (families), ship owners, astronomers, merchants etc. I found out that these are among the best who know this sea, its ports, winds and islands. I asked them about it, its routes and boundaries. I have seen with them books on such matters; these they study, rely upon and act accordingly. This pleased me enormously for I came to sound conclusions. Then I compared what I learned with the drawings I mentioned p r e v i o u s l y . . , etc."

A1-Mokaddasi, an outstanding scientist with a critical mind beyond his time, was not contented with what he read in books or saw on charts, but wished to have a first hand information of the Indian Ocean. His narrative also reflects another important conclusion viz., that Arabic scholars, already in the 10th century were relying upon direct observation and experience and began to question classical Greek theories and charts about the seas.

Arabian nautical instructions for the Indian Ocean appeared again in the 15th cen- tury. The texts of InN MAGID (1490) and SOLAYMAN AL MAHRI (1511)referredto previously, are important documents on astronavigation and include several interest- ing observations on winds, currents, reefs, etc. (ALEEM, 1966).

Among these, reference is made to the southeast trade winds in the Indian Ocean by IBN MAGID. The following account is translated from his book entitled Kitab al Fawayed f i Osul Ilm el Bahr wal Kawaid (" Book of useful instructions and principles of the Science of the Sea ") which he wrote in 1490 A.D. (p. 46-b).

" One of our discoveries is the wave of the Cross (Southern Cross). We have stated that this wave has always an uninterrupted wind similar to the Kus (western wind) in Zofar (port in South Arabia) which is uninterrupted all the year round except for 40 days."

REFERENCES

Arabic texts ABOUL-FEDA, EMADUD D1N ISMAIL (1321) Takweem ul Buldan (cf. REINAUD and DE SLANE). AL BERUNI, ABUL RAYHAN MOHAMAD (ca. 1000) AI Athar al Bakiyah (cf. SACHAU). AL DIMISKI (ED-DIMICHQUI), Shams ed Din Abu Abdullah Mohamad (ca. 1325) Nukhbat

ad Dahr etc. (cf MEmU~N). AL EDRISI, ABU ABDALLAH MOHAMAD (1154) Nuzhat al Mustak (cf. JAUBERT). AL MASSOtn3I, AaUL HASSAN InN HUSSEIN (947) Mourug el Dahab, (cf. BARBmR DE MEVNARD). AL MOKADDASI, SHAMS AD DIN Anu][ABDULLAH MOHAMMUD (985) Ahsan at Takaseem

(of D~ GOVo-E). AL MAHRI, SOLAYMAN AHMAD (1511) (cf. FERRAND). IBN AL FAKIH, AHMAD AL HAMADANI (902) Kitab al Buldan (cf. DE GOEJE).

Concepts of currents, tides and winds among medieval Arab geographers in the Indian Ocean 463

IBN KHORDAZBEH, ABUL KASIM OBAIDULLAH (ca. 846) Kitab al Masalik wal Mamalik (cf. DE GOEIE).

IBN MAGID, SHmAB ED DIN AHMAD (1490) Kitab al Fawayed (cf. FERRAND). SOLAYMAN AT TAGIR (The Merchant) (851) (cf. FERRAND).

Foreign literature ALEEM A. A. (In press) Ahmad ibn Magid, an Arab navigator of the 15th century and his

contributions to marine sciences. First Internat. Congress o f the History o f Oceanography, Monaco.

BARBIER DE MEYNARD C. (1861-1877) A1 Masoudi (Al Massoudi), Les prairies d'or. Texte et traduction par C. Barbier de Meynard I-IX. Paris.

DE GOEJE M. J. (1885) Bibliotheca Geographorum Arabicorum edidit M. J. DE GOEJE. Part V-- Ibn al Falkih. Lugduni Batavorum.

DE GOFaE M. J. (1889) Op cit. Part VI-- Ibn Khordazbeh. DE GOEJE M. J. (1906) Op cit. Part III Al Mokaddasi (2nd Edn.). FERRAND G. (1921-3) Instructions nautiques et routiers Arabes et Portugais des X V e et X V I e

si~cles. Tom 1--Le pilote des mers l'Inde, de la Chine et de l'Indonesie par Shihab ad Din Ahmad ibn Majid dit " l e lion de lamer . " Text Arabe, reproduction phototypique du Ms 2292 de la Biblioth6que Nationale de Paris, Paris.

FERRAND G. op cit. Tom. II--Reproduction phototypique des Instructions nautiques de Solayman al Mahri (Ms. 2559). Paris.

FERRAND G. (1922) Voyage du Marchand Arabe Solayman. Paris. JAUBERT P. A. (1836-1840) Gdographie d'Edrisi traduite de l' arabe en franeais d' apr~s deux

manuscrits de la biblioth~que du roi et accompagn~e de notes par P. A. JAUnERT. I-II . Paris. LEWICKI T. (1936) Les premiers commereants arabes en Chine. Rocznik Orientalisticzny.

XI pp. 173-186. Kxakow. MEHREN A. (1923) Collectio editionum rariorum orientalium II, Ed. DIMXCHQUI (cosmographie)

published by A. Mehren. Leipzig. REINAUD P. T. et M. (3. DE SLANE (1840) Gdographie d'Aboulfdda. Texte Arabe publi~

d' aprbs les manuscrits de Paris et de Leyde aux frais de la Socidtd Asiatique par M. Reinaud et Mac Guckin de Slane. Pads.

SACHAU C. E. (1923) Chronologic orientalisher Volker yon Alberuni. Edited by Dr. C. EDUARD SACHAU (New Edn.). Leipzig.

WARREN BRUCE A. 0966) Medieval Arab references to the seasonally reversing currents of the North Indian Ocean. Deep-Sea Res., 13, 167-171.