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國立清華大學歷史研究所乙組
碩士論文
Fettering the Stars:
Islamic Navigational Knowledge in Ming China
牽星術:明代中國的伊斯蘭導航知識
研究生: 林筱倩 (Hsiao-chien Lin)
學號: 101043513
指導教授: 王憲群 (Hsien-chun Wang)
中華民國一○四年六月
i
摘要
宋元以來,伊斯蘭世界與中國之間,藉由成熟的海洋技術而有著頻繁貿易的往來,
不同文化之間的交流亦隨之興起。在中國航海史上著名的航海家鄭和(1371‐1433),曾
在十五世紀初期帶領著船隊七次下西洋,航程遠至非洲東岸。歷史材料提及鄭和船隊可能
利用一種名為「牽星術」的導航技術,並使用一種名為「牽星板」的導航儀器。藉由這樣
的儀器,導航員可在夜晚中測量星體和地平線的仰角,並以「指」為測量單位,了解船隻
的位置,以成功達到越洋航行的目的。本論文主旨即在探討這種導航技術與儀器背後的多
文化語言與天文知識的基礎。
我發現在遠洋航行中,水手必須熟練於時間的掌握及方位的辨識,他們藉由觀察星
體的運行來解決這兩個問題。而在印度洋及阿拉伯海之中,使用泰米爾及馬拉姆語的水手
們,便相當善於運用這樣的導航技術。這樣的技術藉由星體仰角的高度來判斷時間,並以
zām 為單位。zām 是一種古代印度計算時間的方式,主要使用特定亮星及月亮做為觀測
的依據,測量出 「指」,阿拉伯語為 isba 同樣為手指的意思。配合,(إصبع) zām 的計時方
式,得以在汪洋大海中了解航行所花費的時間。水手們更利用在黃昏或清晨時分,藉由亮
星於海平面的位置,來判斷方位。除此之外,在儀器的使用上,類似「牽星板」的航海儀
器有著多種形式的存在。例如,水手在測量的時候,可以使用相同的板子但運用不同的結
點,或者使用不同大小的板子,但繩長不變,亦或是板子大小不同且同時隨結點改變。在
中國史料中,明代李詡《戒庵老人漫筆》等材料顯示,牽星板是一組由十二塊大小不同的
木板組成,顯示華人地區所使用之「牽星板」為板子多塊的類型。而在中國的歷史材料
《武備志》中,除了記載此項航海技術的遺跡,也標示著稱為「針路」的中國傳統航海方
式。此種特殊的繪圖方式,即說明多種文化的導航知識存在於這條航線上。另一方面,我
們亦可從使用方式和儀器的名稱上窺見知識的流動,例如「牽星」一詞在阿拉伯語中為
al‐qaid 同為牽引的意思,為一種記憶天體相對位置的特定記憶方法。令人驚喜的,(تكبيل)
是,更多語言關連如同「牽星」和「指」的例子,隨著航海技術的達發而存在於此條航線
中。綜合以上而言,不論從史料或是語言翻譯上,都可以看出跨文化知識傳遞的軌跡。
ii
最後,我根據《前聞記》的航程記載,逐步說明鄭和越洋航行之時所使用的導航知
識。發現船隊利用季風做為動力,於冬季利用東北季風出發,並順著夏季的西南季風回程。
此外,從《武備志》裡「過洋牽星圖」的記載中,了解船隊主要仰賴現今北極星、昴宿星
團、北河三、南河三、老人星和南十字星,以確認船隻在固定緯度的航線之上。與此同時,
導航員利用「牽星板」等相似儀器,除了確認船隻所處緯度,更測量星體在天空仰角的變
化,搭配 zām 這種計時方式而得知航行時間。
因此,本論文認為,此類航海技術的發展非一蹴可及,鄭和並非第一位於此條航線
上航行之人,鄭和下西洋所使用的導航技術,乃是一個多文化交流之下的成果,包含著伊
斯蘭、印度、與中國等不同文化的導航技術。因此,鄭和的壯舉,其實是多文化交流之下
的結果。
iii
Abstract
Beginning from the Song and Yuan Dynasties, Muslim and Chinese ships frequently sailed
the south China coast, Southeast Asia, Sri Lanka, and the Persian Gulf, trading goods and
cultures. The Chinese naval commander Zheng He 鄭和 (Cheng Ho, 1371‐1433) lead seven
expeditions along these sea routes, sailing as far as the east coast of Africa in the early 15th
century. Historical sources mention that Zheng He used a navigation method called qianxing shu
牽星術, which employed a particular instrument named qianxing ban 牽星板. Navigators could
use this instrument to measure the angle between stars and horizon to find units of zhi 指. They
used this technique to understand the location of their ships while sailing in the open‐sea. This
thesis discusses the linguistic connections between different cultures and the astronomical
knowledge behind that technology.
Time and direction were essential to this maritime technology, and this technology united
these two issues by observing stars. This technique relied on the altitudes of stars and horizon
to define time. Moreover, it used zām, which was a special time‐measurement system in
ancient India, as a unit of time and measured the specific bright stars and the moon in terms of
zhi 指 in Chinese and isba (إصبع) in Arabic. Both words mean “finger.” Also, navigators observed
the bright stars on horizon in dawn and dusk to understand directions. This technique employed
the instrument qianxing ban, which can be classified in different types: those with knotted
strings and a single board, those with unknotted strings and boards of different sizes, and those
with both knotted strings and different sizes of boards.
By the seventeenth century, a treatise on armament technology reported that Chinese
sailors carried magnetic‐needle routes marked with gen 更. These maps were typical of
traditional Chinese maritime technology, but also contained information about the stars in
terms of the unit zhi which was familiar to most sailors in the Indian and Arabic Oceans. Thus,
these sea‐charts prove the cultural interactions on this sea‐route.
Finally, Zheng He’s voyage is reconstructed. Zheng He’s fleet exploited the power of the
monsoon. They relied on the northeast wind to depart in winter, then followed the southwest
iv
wind to return to China in summer. Moreover, Zheng He’s navigators relied on the altitudes of
Pole Star, Pleiades, Pollux, Procyon, Canopus and Southern Cross for directions. In this way,
sailors could keep on the right route. Meanwhile, they used qianxing ban to measure the angle
of stars. They also used the zām time‐measurement system to measure time. In conclusion, the
qianxing shu and qianxing ban were the result of centuries of cultural communications between
China, India, and the Islamic world.
v
Contents
Int roduct ion……………………………………………………1
Navigational Skill and Lunar Mansions………………7
Introduction…………………………………………………………………7
History of Navigation…………………………………………………….8
Chinese Navigation……………………………………………………….9
Arabic Navigation……………………………………………………….14
Isba and Zām…………………………………………………………..….17
Navigation methods…………………………………………………...23
Qiyas………………………………………………………………………………….….23
Fettering…………………………………………………………………………….….25
Abdā l…………………………………………………………………………..…………26
vi
Navigational Miscellany………………………………………………..……….27
Monsoon……………………………………………………………………28
Monsoons of the Arabian Sea………………………………………………..28
Monsoons of the Indian Ocean………………………………………………28
Lunar Mansions………………………………………………………….32
Definition of Lunar Mansions……………………………………..32
Simple Astronomy………………………………………………………………….33
Development of Astronomy……………………………………………..…...35
Lunar Mansions in different cultures………………………….45
Astronomy: Mansions mark day of month……………………………..51
Connection of Lunar Mansions to Navigational Astronomy……53
Use of Lunar Mansions in Time‐Keeping…………………………….….54
Conclusions…………………………………………………………….….55
How to Use Lunar Mansions………………………………………………….55
Relationship with Navigation……………………………………………..….56
Instruments………………………………………………..…..60
vii
Introduction………………………………………………………….……60
Compass Rose and Magnetic Compass…………………….…62
A. Magnetic Needle Compass (Chinese)…………………………….…..64
B. Zām compass (India, Arabic)………………………………………….…..68
Astrolabe……………………………………………………………….…..75
History, Greek to Arabic…………………………………………………….…..75
Parts of the Astrolabe…………………………………………………………...76
Uses of Astrolabe…………………………………………………………….…….83
Results, latitude, and time…………………………………………………..…88
About Qianxin ban and Liangtian chi …………………….…..89
The Liangtian chi……………………………………………………..…90
What is the Qianxin ban……………………………………………..94
A. Knots………………………………………………………………………………...95
B. Different sizes………………………………………………………….……..101
C. Different Sized Boards with Knots……………………………..…….101
Conclusion……………………………………………………….……..102
viii
Zheng He……………………………………………………….105
Introduction……………………………………………………….….…105
Background………………………………………………………….…..106
How Did Zheng He Succeed in His Voyage?.................112
Linguistic Connections………………………………………………125
Development of Instruments……………………………………127
Conclusion……………………………………………………………….131
Conclusion…………………………………………………….135
Reference………………………………………………………141
‐ 1 ‐
IntroductionIn the fifteenth century, the Ming Dynasty eunuch admiral Zheng He 鄭和(1371‐1433)
commanded seven expeditionary sea voyages to southeast Asia, South Asia, and even eastern
Africa. Historians hail the voyages as China’s greatest achievement in overseas exploration.
Actually, though, this sea‐route had developed generations before Zheng He’s voyage. For
example, Faxian 法顯 (337‐422) had traveled in search of classical books on Buddhism. In
Faxian’s account, he described the sea route by reporting locations and the number of days of
travel between them. The sea‐route he described streched from Sri Lanka to the strait of
Malacca and back to Guanzhou 廣州. 1 This last location, Guanzhou, was an important harbor
which had been developed in Southern Song Dynasty by foreign merchants.2 As the account by
Faxian illustrates, this sea route had been traveled for several generations before the Ming
Dynasty. Nevertheless, historians are unable to explain how, in terms of navigation, admiral
Zheng and his mariners managed to sail across the Bay of Bengal or the Arabian Sea. They often
mention a technique called “star‐fettering” (qianxing 牽星) but cannot agree how it worked.
Clearly, this star‐fettering technique demands further research and, given the Western
destinations of Zheng He, a possible coordination with Islamic origins.
Until the Ming Dynasty, the great Zheng He expedition represented the high point of
maritime technology. However, because such voyages had been possible for several generations,
it is more interesting to ask what kind of conditions could produce these voyages. Ming Dynasty
mariners might have used the stars as a guide. According to a twelfth century record of China’s
maritime trade, the Phingzhou Table‐Talk (Pingzhou Ketan 萍洲可談, 1191), mariners certainly
used the stars as a guide: “Navigators know geography. [They] observe the stars at night and the
sun in the daytime, and [they] use the compass on cloudy days. (夜則觀星,晝則觀日,陰晦
1 Ding, Qian 丁謙, 1971, p.10B‐11A. 2 Kuwahara, Jitsuzo 桑原騭藏, 1971, p.30.
‐ 2 ‐
則觀指南針).” 3 Unfortunately, this passage does not provide any practical information about
how the stars could be used as a guide and whether any instruments were involved.
Slightly more information, especially about Zheng He’s voyages, can be found in a
seventeenth century military treatise, Treatise on Armament Technology (Wubei zhi 武備志,
1621). This book contains a set of schematic charts showing Zheng’s routes from Nanjing, the
administrative stronghold in east China, to Qeshm Island in the Strait of Hormuz. The term zhi
(finger 指) appears next to the dotted lines after certain digits, indicating that it is a navigational
unit.4 (Figure 1) The treatise also includes a set of four diagrams entitled “the Chart of Sea‐
Crossing by Fettering Stars (Guoyang qianxin tu 過洋牽星圖 , 1621), which show how
constellations could have guided Zheng He’s fleet from Sumatra to Sri Lanka and Calicut to
Hormuz.5 (Figures 48 and 50)
The terms zhi (finger) and qianxing (star‐fettering) are intriguing. A sixteenth century
notebook (biji), Casual Notes of the Old Man of the Discipline Monastery in Elite Theater (Jie’an
laoren manbi 戒庵老人漫筆 1597) by Li Xu 李詡 (1506‐1593), includes a passage entitled
zhoubi suanchi 周髀算尺. It is not clear what the zhoubi suanchi is or whether it has anything to
do with the ancient mathematical treatise The Arithmetical Classic of the Gnomon and the
Circular Paths of Heaven (Zhoubi suanjing 周髀算經, about First century B.C.). One more
sixteenth century source shows that the term zhi relates to navigation. Record of the Tributary
Countries of Western Oceans (Xiyang chaogong dianlu 西洋朝貢典錄, 1520), a book which
records Ming China’s communication with foreign countries, vaguely suggests that, in order to
sail to the Kingdom of Liushan (溜山國), now the Maldives, one has to sail according to the Pole
Star and take a certain number of digits of zhi as the reference point in their voyage.6 However,
the text does not tell us exactly how the technique worked.
The available Chinese sources also seem to suggest that at least by the fifteenth century
Ming Chinese navigators used a kind of navigational tool, called “star‐fettering boards” (Qianxin 3 Zhu, Yu 朱彧 1191, p.1644. 4 The charts are named “Zheng He’s Sea‐Chart from Nanjing to Foreign Countries” (Zi Baochuan Chang Kaichuan Chang Cong Longjiang Guan Chu Shui Zhida Waiguo Zhufan Tu 自寶船廠開船從龍江關出水直抵外國諸番圖). 5 Mao, Yuanyi 茅元儀 1621 , p.319. 6 Huang, Shengzeng 黃省曾, 1520, unpaginated.
‐ 3 ‐
Ban, 牽星板) to measure the angle between the horizon and certain constellations in units of
zhi and jiao. Historians of Chinese science argue that both the star‐fettering technique and the
boards might have an Islamic origin.7 In his examination of the Wubei Zhi, George Phillips
pointed out that the technique of using zhi to measure the angle between the horizon and the
stars was also used by the Moorish pilot engaged by Vasco de Gama in the early sixteenth
century.8 Yen Dunjie 嚴敦杰 argueed that the star‐fettering technique originated from the
Islamic world and that one zhi equals to 1 36/60 degrees.9 Joseph Needham suggested that
fifteenth‐century Portuguese sailors, who were under Islamic influence, might have used a
similar technique. He also noted that the Islamic instrument, named the kamal, was similar to
the star‐fettering boards.10 However, some Chinese historians have argued that the boards
evolved out of an ancient Chinese instrument named the “heaven measuring ruler” (liangtian
chi 量天尺).11
This argument about the Heaven Measuring Ruler is implausible. Different kinds of
astronomical instruments, mainly sundials, have been named Heaven Measuring Rulers but
have nothing to do with navigation. Although it is possible that a certain kind of Heaven
Measuring Ruler was used as a navigational tool, there is no evidence showing how it
functioned.
Thus, since the sources had connections with Western culture, these sources should be
related to other civilizations which were on this sea‐route. Firstly, modern scholars have studied
the communication between the Islamic world and China. For example, Su Liangbi 蘇良弼12
mentioned that from the beginning of the Song Dynasty, there were mosques in Quanzhou, the
most important port for those doing business with the Islamic countries. The cultural exchange
started well before the Song Dynasty. It is known that Ibn Wahab el‐Basri met the Chinese
emperor in A.D. 876. El‐Basri travelled from the Red Sea and the Persian Gulf to do business in
7 Yan, Dunjie 嚴敦杰, 1966, p.77‐88. 8 Phillips, George, 1898, p.219‐220. 9 Yan, Dunjie 嚴敦杰, 1966, p.77‐88. 10 Needham, Joseph, 1954, p.574. 11 Wang, Lixin 1983, p.122‐189; Hangyun Shihua Bianji Xiaozu 航運史話編輯小組, 1978, p.170‐189. 12 Su, Liang Bi 蘇良弼, 1988, p.81.
‐ 4 ‐
China. Similarly, Yang Waizhong 楊懷中13 has stated that from the eighth to fifteenth centuries,
Arabian sailors had trading businesses across the ocean, and that Chinese Muslims were experts
in navigation starting from the Yuan Dynasty.
Wei Dexin 魏德新14 has discussed some Chinese Muslims who traveled together with Zheng
He. One of them, named Wang Jingheng 王景弘, was a Chinese Muslim and an expert sailor of
the Ming Dynasty. In addition, Ma Huan 馬歡 recorded the landscape, the local environment,
and culture in his book Yiya Shenglan(瀛涯勝覽, 1451) . Fei Xin 費信 (1388‐?), who collected
local information and preserved the descriptions of different countries in the book Xengcha
Shenglan (星槎勝覽, 1436), also travelled with Zheng He. All of these writers were Muslims.
In addition to Chinese travelling to Arabia, Muslims gained greater influence in China than
they had before. The most visible figure of Arabian descendant was named Pu Shougen 蒲壽庚
(1245‐1284). He managed foreign ships and businesses in Quanzhou from 1250 to about 1275.
The Pu surname was a strong clan in Quan Zhou. They were a famous Chinese Muslim
family and were experts at interacting with Muslim merchants. Wei Dexin argues that Pu Rihe 蒲
日和, Pu Shougen’s nephew, also travelled with Zheng He and played an important role in his
voyages.
Zheng He was also born into a Muslim family. The emperor ordered Zheng He to relocate to
Quanzhou. Chen Guoqiang 陳國強 shows that because he was a Muslim, Zheng went regularly
to mosques to pray. From Quanzhou, he traveled to the Western Regions with Pu Rihe and other
Muslims of Quanzhou. Apparently, Zheng had strong connections with Islamic culture and most
likely was familiar with the Islamic technology, especially as far as navigation instruments are
concerned. 15
Zheng He’s Islamic background could have played an important role in obtaining
navigational knowledge. According to the historian of Islamic culture Paul Lunde, the famous
sailor Ahmad Ibn Mājid used the Pole Star to determine the latitude. Ibn Mājid could measure
its height above the horizon and relate that height to latitude. Keeping the Pole Star at the same 13 Yang, Waizhong 楊懷中 2005, p.191. 14 Wei, Dexin 魏德新 2005, p.233. 15 Chun, Guoqing 陳國強 1988, p.126.
‐ 5 ‐
height would be equivalent to sailing from east to west or back on same latitude. Ibn Mājid also
mentioned that to measure of the Pole Star’s height above the horizon, sailors used something
called the “kamal” (كمال ). Portuguese sailors had found latitude by measuring the altitude of the
sun. This method was influenced by Arabian sailors of the thirteenth century. Sailors determined
their latitude according to Pole Star, thus to find their longtitude and time, they had to rely on
the zām system and lunar mansions.
The argument that Chinese navigators had Islamic connections holds promise. As George
Phillips has noticed, isba (إصبع) means finger in Arabic, and one isba is equal to eight zām.16 The
terminology is similar to the Chinese system mentioned above. Moreover, G. R. Tibbett has
pointed out that one of the Arabic navigational skills was called “fettering” – al‐qaid .(تكبيل)
Thanks to Tibbett’s commentary and translation of fifteenth century Arabic manuscripts of
navigation, the evidence is clear that Arab sailors measured the distance between the star Aries
and Dibban as four isba, or four times the width of a finger. They also used similar methods to
measure the distance between the stars and the horizon to maintain their courses. When sailing
along the coastlines, sailors additionally used tides, winds, landmarks, coral, plants, or the types
of marine creatures indigenous to the area, as markers of their positions. More importantly,
observing monsoons and ocean currents as well as the positions of the stars and the lunar
mansions would have been crucial for timekeeping and maintaining courses.17
Therefore, to understand how Zheng He and his fellow mariners used the star‐fettering
system and the lunar mansions to sail across the Bay of Bengal and the Arabian Sea, the Islamic
origins of the star‐fettering system must be considered and the astronomical knowledge behind
it must be examined. After such a reconsideration of the evidence, an attempt may be made to
combine Chinese and other civilization sources.
Chapter One will discuss the historical background of China’s communication with the
Islamic world by the fifteenth century. Chapter Two will explain the art of navigation and the
meaning of the isba and zām. In addition, this chapter will explore how Chinese and Arab sailors
might have used the lunar mansions as a means of time‐keeping. Chapter Three examines how
16 Phillips, George 1898, p.219‐220. 17 Tibbetts, G. R. 1981, p.284‐285.
‐ 6 ‐
the instruments such as the compass, the astrolabe, and the quadrant were used in navigation.
Chapter Four tries to explain the navigation of Zheng He’s voyage by simple steps. Moreover,
this chapter presents the different works on navigational knowledge in different cultures along
this sea‐route. Chapter Five presents some conclusions and directions for future research.
‐ 7 ‐
NavigationalSkillandLunarMansionsIntroduction
Navigation has a long history. The Greeks and Romans reported stories about their
achievements in navigation. For example, Herodotus wrote that the Persian king Darius (550‐
486 BC) sent a ship to discover a sea‐route to Arabia and the Persian Gulf.18 To make this
discovery, King Darius asked a Greek sailor named Scylax to find the route from India to Egypt.
Two centuries after Scylax, Alexander the Great asked Nearchus, his navarch or admiral, to
reexplore the same route when he returned the triumphant Alexander from the Indus River in
Pakistan to the port city of Susa in the Persian Gulf. Through the Ptolemaic Era, Egyptian traders
used this familiar route and established Socotra, an island of near the Horn of Africa, as a
trading‐post on the path between Egypt and India. Clearly, Europeans had been trying to reach
eastern destinations for many years. However, unlike their Asian counterparts, a written record
of their navigational techniques has survived.
Each culture has its own method to navigate, and each culture has its own specific method
for sailing. No matter what the method was used in each different culture, the identification of
directions was one of the most important techniques. Moreover, the measurement of time is
also a necessary technique for navigation, especially for crossing the open ocean. Due to having
to measure how long had been sailing, sailors used their particular method to solve this
problem. For example, in the Indian Ocean, they measured the movement of stars to
understand the passage of time. These methods of telling time can be traced for long time to
show how notions of time developed in different cultures. The notion of measuring of time also
included the methods and units of counting time. For instance, Chinese used double‐hour, on
the other side of the water, Indians and Arabs used zām (زام).
The zām is a special and unique method to measure time by the movement of stars. This
method relies on the observation of experiences from several generations. Ancient astronomers
observed sun and moon’s orbit. They found the paths and times of their circles and understood
18 Herodotus, Histories, 4.44.
‐ 8 ‐
time passing. For navigation, sailors did not have to be as precise as astronomers who made
calendars. However, the sailors used the observation of stars as a reliable method to
understand time.
Since these bright stars and constellations have strong connections with time‐measurement,
some maritime technology developed for methods of guiding boats by stars. At least three
methods, the fettering of stars, the qiyas, and the abdāl, comprised the maritime technology for
guiding by stars. These technologies were all popular in Indian Ocean and several civilizations
were connected in communication by their travels in the Indian Ocean.
Therefore, returning to Zheng He’s famous voyage, the fleet departed from Nanjing 南京
and followed the coastline until Southeast Asia, crossed the Indian Ocean and arrived in the
Persian Gulf. In this way, they encounted several cultures on this famous sea‐route. Thus, the
different maritime technology of Chinese and Islamic cultures must be considered. Because
time‐keeping is an important part of maritime technology, the different methods of time‐
measurement and the use of the lunar mansions must be explained.
HistoryofNavigationGreeks used stars (and winds) to describe their bearings from the Homeric era until Roman
times.19 Other early accounts consider the rising times of the stars and coordinated them with
latitude. The early sources on navigation report that the first person to find the direct path to
India was Hippalus. Pliny the Elder explained the report by clarifying that Hippalus discovered
the uses of the monsoon wind and named it the “Etesian wind.”20 By this account, Hippalus was
the first to understand the cycle of the winds and use them to return. Obviously, this story
occurred before Arabs developed their sciences of navigation. Although first‐century European
accounts describe Hippalus as the discoverer, when Arya Sura wrote the Indian Jatakamala,
contemporaneous with the Periplus in first century A.D., he described the arts of pilots and
navigators. Arya Sura described the early navigational skills that used bright stars but he also
descibed the Bodhisattva as a pilot.
Accordingly the High‐minded One possessed every quality required in such a one. Knowing the course of the celestial luminaries, he was never at a loss with respect to the regions of
19 Homer, Iliad,2.145, 9.5, 11.306; Homer, Odyssey, 5.295. 20 Pliny the Elder, Natural History, 6.23‐.26.
‐ 9 ‐
the sky; being perfectly acquainted with the different prognostics, the permanent, the occasional, and the miraculous ones, he was skilled in the establishment of a given time as proper or improper; by means of manifold marks, observing the fishes, the colour of the water, the species of the ground, birds, rocks, and so on, he knew how to ascertain rightly the part of the sea; further he was vigilant, not subject to drowsiness and sleep, capable of enduring the fatigue of cold, heat, rain, and the like, careful and patient. 21
This description is a clue that religion, like trade, could also have an important connection with
navigation.
ChineseNavigationThis thesis does not focus on Chinese navigation, but it is must say a few words about it.
Navigation is only as precise as the needs of the traveller. For example, a map from a 1621
military treatise Wubei zhi 武備誌 presents the itinerary of Zheng He without providing
longitude and latitude. Most of the information shown in this map is just mountains and rivers.
In addition, the zhenlu 針路 (compass‐needle route), or the distance measured using the twelve
traditional watches, or “double hours,” is also an important part of the information presented
here. If this kind of map was used, the ships must have sailed along with the coastline. However,
because Zheng He used navigational tools in his voyages, he must have used different kind of
maps and navigational skills.
For regular human activity, it was safer to follow the coastline and the groups of islands and
sail there than enter the open ocean. Moreover, there was no reason to doubt this navigational
knowledge which had been accumulated from sailors by generations. Zhenglu is a kind of
navigation method developed especially by ancient Chinese. This maritime technology arose
along with the development of the needle compass. According to the magnetized needle made
of lodestone which was placed above the compass rose, sailors not only realized directions, but
also rely on the record of maps to understand the sea road. For example, the marks on the
Treatise on Armament Technology (Wubei zhi 武備志,1621) recorded readings of the compass
needle with a dotted line and told sailors the waterway and directions.
21 Arya Sura, Jatakamala, 14, translated by J S Speyer (first published 1895)
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Figure 1: Selection from Treatise on Armament Technology (Wubei zhi 武備志,1621). The red oval contains the text “滿剌加開船用辰巽針五更.” (Using the chenxun needle to sail from Malaca.)
In addition, these vestiges of the zhenlu can be found not only on the sea charts, but sailors
also wrote them down and made something like a guide book for navigation. Versions of these
books were called the Book of Zhenlu (Zhenlu Bu 針路簿,) or Book of Genglu (Genglu Bu 更路
簿). These old books collect and record maritime experiences from sailor’s lifetime. They could
even accumulate experiences from several generations of the same sailing family.
Navigation by the compass needle methods can be traced from Yuan Dynasty in The
Customs of Cambodia (Zhenla fengtu ji 真臘風土記, 1312.) The Zhenla 真臘 in this title is the
ancient name of Cambodia. According to this record, some water paths were indicated by
readings of the compass needle:
又自占城順風可半月到真蒲,乃其境也;又自真蒲行坤申針,過崑崙洋入港…22
22 Zhou Daguan 周達觀, 1966, p.1A
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Sailing with the wind from Champa can take half a month to arrive at Myanmar, and this is
just at its border. And going from Myanmar the compass need reads kun shen (roughly,
southwest) via Kuanluan Ocean into the harbor.
The usefulness of the method led to its popularity and it was still used in the Ming Dynasty.
福州五虎門開船,用乙辰針取官塘,船行三礁東西邊。用丙午針,取東沙山。23
Sailing out of Fuzhou (the capital of Fujian province), Wu Humen, use yichen (roughly
southeast) for the compass needle toward Guantang, with the boat passing three reefs on
the east and west side. Use biengwu (roughly south‐by‐southest) for the compass needle
toward the Dongsha mountain.
Sources such as these can still be found nowadays. The Book of Zhenlu, was incorporated
into the “Maritime Guide” (Hanghai Zhinana, 航海指南, 1965). This book was compiled by
Quanzhou Maritime Museum and preserves the accounts from local sailors. This book
contained maritime technology such as tides, winds, and the situation of water flow in different
seasons. Moreover, it included lots of terminology used by the sailors. One of these technical
terms is zhen 針 which means the direction of the compass needle. In addition, this book
describes the shape of mountains or islands which would be seen by sailors as they navigated.
23 Chen, Jiarong, Zhu, Jianqiu 陳佳榮、朱鑒秋, 2013, p.69.
‐ 12 ‐
Figure 2: Image from the Hanghai Zhinana. A description of Mount Tai‐dun and surrounding locations. Sailors recorded descriptions of the landscape such as these to identify their location.
‐ 13 ‐
Figure 3: Selection from the Hanghai Zhinana, unpublished. This figure was taken from a copy preserved at the Quanzhou Maritime Museum. This page describes the magnetic‐needle route of navigation along the coast line. It describes the return from Xiamen to Hainan Island in the South China Sea, and another route from Taiwan to Penghu Island. It records the navigational information, including the jiayin zhen 甲寅針 and chouwei zhen 丑未針. These notes represent the details of the Chinese magnetic‐needle navigation method.
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ArabicNavigationThe geographic knowledge used by navigations was no fossilized cultural import. Arabs
used Ptolemy’s geocentric astronomy to compute the positions on the earth. The degrees of
longitude (distance along a north‐south line) which separated two cities could be determined by
the height of the Pole Star. The degrees of latitude (distance along an east‐west line) could be
found by differences in the observed times of eclipses. Because Arabic astronomers predicted
the sun’s position and calculated eclipses by the techniques described in Ptolemy, they could
enlarge and update his Geography with their travels. This information was useful for religious
reasons: From ninth to fourteenth century, Arabic astronomers worked to calculate the qibla,
which is the direction of Mecca from a given locality. The final result of these investigations
greatly improved trigonometric knowledge.
Not only did the requirements for prayer determine the Muslim conceptions of geography,
the requirement that prayers be offered at certain times created the Muslim conception of time.
According to the Koran, observant Muslims needed to offer ṣalāh or ritual prayers The ,(صالة)
times of these prayers were astronomically determined. These times are just after sunset
,العشاء) maghrib) when the day begins, according to the Muslim calendar, around nightfall ,المغرب)
isha) when the stars can first be seen, at dawn (الفجر, fajr), just after midday or noon (الظھر, zuhr),
and in the afternoon asr). Thus, observant Muslims who prayed regularly also became ,العصر)
well‐practiced in astronomical timekeeping, including both calendrical measurements and the
observation of hours by day and night. Because prayers were a public practice, the Muslim
conceptions of time and space extended beyond the limited circles of astronomy.
Moreover, Muslim astronomers knew how to determine latitude and longitude from
observations of the azimuth24. As Arabs converted and standardized an increasingly large
empire, they adopied the intellectual traditions of the people they encountered. Thus, Arabic
astronomy was influenced by Indian philosophy, such as the Siddhantas of Aryabhata and
Brahmagupta, from the eighth century. Indian astronomy had been translated into Pahlavi in
24 An arc of the horizon is measured between a fixed point and the vertical circle passing through the center of an object. In astronomy and navigation, this arc is usually measured clockwise from the zero at north through 360 degrees.
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order to write the Zij‐i Shah, or the Astronomical Table of the King, which was produced in the
ninth century. In short, Arabic astronomers played an important role by absorbing Indian
knowledge and western techniques. As a result, they developed good astronomy and navigation.
Some portion of this knowledge travelled with the merchants who probably relied on the same
route that Faxian took.
Thus, thanks to Tibbetts, the description of navigation by the famous Arabic sailor named
Ibn Mājid (1421‐?) has been translated.25 In his introduction to this translation, Tibbetts
summarized navigation on the Indian Ocean before the time of Ibn Mājid. Ibn Mājid identifies
twelve “useful things” فائدة) fā i͗da) and gives a chapter to each of them in this book. By Ibn
Mājid’s style of composition, the “useful things” are lessons on navigation, rather than tools or
elements of navigation:
1. How to use compass points and lunar mansions. In this part of his book, Ibn Mājid mentioned
rhumbs and zām (زام). In modern Chinese studies, zām is mentioned several times, however, no
one explains clearly what the zām is. In the first chapter, Ibn Mājid explained it is unit for
distance.
2. A summary of the basic principles of the sea. Ibn Mājid includes lunar mansions, rhumbs,
route distances, latitude measuring, signs of land, the seasons of the sea, the instruments of
ship among the second chapter.
3. Lunar mansions. Here, Ibn Mājid focused on explaining the lunar mansions. A lunar mansion
is a part of the ecliptic, through which the moon orbits around the earth. Ibn Mājid explains the
names and locations of all twenty eight constellations, tells after how many days each mansion
rises and sets, and names the bright star in each mansion. Knowing the days on which each star
rises into the sky is an important technology for sailors to avoid getting lost.
4. Compass rhumbs. There are nine compass rhumbs which Ibn Mājid names from north to
south but he identifies number three pair, al‐Naʿsh and Suhail, as especially good. In his
discussion of these rhumbs, Ibn Mājid makes mention of the iṣbaʿ and concludes that this is the
best way to measure latitudes throughout the whole of the Indian and Arabian coasts. Ibn Mājid
also used the “fettering” to figure out the directions for setting out for lands in Sind, Bengal, 25 Tibbetts, G. R. 1981 p.68.
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China and Red Sea. Here, “fettering” means to tie, or prevent from moving. The Chinese word
qian 牽 also has this meaning. Moreover, as Ibn Mājid described, this method of fettering is
very similar to the method used to sail in the Arabian Sea. For every iṣbaʿ of increase in the
height of the pole star, sailors shoud know the change in latitude.
5. Ibn Mājid gathers several topics into a chapter: stars used as extra rhumbs, other works on
astronomy and geography, the Roman months, and the planets. In this chapter, Ibn Mājid
mention the planets as days of the week and discusses the planets, but does not relate them
directly to navigation.
6.Three sorts of sea route. Ibn Mājid names three types of sea routes. The first one is the route
along the mainland, the path of trade (dῑrat al‐mul, مول The second one developed from .(ديرة
the dῑrat al‐mul and was called the absolute path of (dῑrat al‐maṭlaq, قديرة مطل ) by which the
ships enter or leave by using measurements. The third path is the path of necessity (dῑrat al‐
iqtidā ,͗ ديرة اقتضى ) which is based on calculations from familiar places. In this case, the ships set
out from a geographically known place and travel toward a geographically know place.
7. The Maldives and South‐East Asia. In this chapter, Ibn Mājid describes measurements
according to the Little Bear, the constellation Ursa Minor. He explains the latitude of Ceylon by
measurements of the pole star. Moreover, he introduces latitude measurements from the Red
Sea and discusses common failures in taking latitudes.
8. Oceanic environments. Ibn Mājid describes typhoons, other occurrences at sea, seaweed,
birds, and how to use these environments on a voyage.
9. Description of the coasts of the world, and measurement of the earth.
10. A geography of places like the Arabian Peninsula, Madagascar, Sumatra, Java, Ceylon, and
Zanzibar.
11.Seasons. Ibn Mājid reports the seasons which are suitable for beginning a voyage and for the
return.
12. Sea routes, unclear areas, and dangers.
Other information on the navigation theory in the fifteenth century Islamic world comes
from other sources. In Alfred Clark’s paper “Medieval Arab Navigation on the India Ocean:
Latitude Determinations,” he classified four ways that Arabs checked their latitude in Medieval
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times. The first way was to use the pole star. The latitude can be determined from the angle
between the Pole Star and horizon. The second method was called a “single star on the
meridian.” The meridian makes an imaginary line from north to south. The Pole Star or other
bright stars will stand along on this line. This meridian line can be used as a standard to check
the distance from other constellations. From these measurements, the latitude can be known.
The third way is “substitutes”, (abdāl, ابدال). By this way, the measurer must chose two stars,
equally symmetric in altitude along the meridian. Finally, the last way of determining latitude is
“fettering” (al‐qaid, قيد). Obviously, according to experience, the measurer of the latitude could
follow the bright star to find another bright star. Because the location of these two stars on
celestial sphere is known, the measurement can be related to the latitude. This way of knowing
latitude is more complicated, but it can be useful because it can be used even when the pole
star can’t be measured because of clouds.
Ancient Arabic navigational techniques show a rich knowledge of navigation. A deep
understanding of these techniques seems to be a necessary condition for navigating by stars.
Hence, in the paragraphs below, the units of measure for navigation in the Indian Ocean, and
relate these units to a set of simple skills for navigating by the stars.
IsbaandZāmIn Arabic, an arc measured in the sky could be called either tirfa (ِاْلِتَواء , a loanword from
Latin curva, curve) or isba. A navigator measured the angle between the Pole Star (or a bright
star, or pair of bright stars, as Clark described) and the horizon at a given time. In Arabic, the
word isba means “finger.” When used in a navigational sense, an isba is a unit of measure for an
arc on the surface of the celestial sphere. Although this name of this unit may have originated
from the practice of navigators measuring with their hands, the value of the unit represents
almost exactly on modern degree. Moreover, because the arc represents the unit of the angle
between horizon and Pole Star, it also represents a unit of latitude. These units were the basic
measurements for the navigators, but they also subdivided them. Some studies explained that
measurement of the degree, one isba is also equal to eight zām. For example, George Phillips
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has suggested that in Arabic isba means finger and one isba is equal to eight zām.26 In addition,
Tibbetts reported that Arab sailors measured the distance between the star Aries and Dibban as
four isba, which means four times the width of a finger.27
Today, scholars debate exactly how many of these units equal corresponded to a
modern degree.28 Yen Dunjie has inspected the markings on instruments to find that 1 isba
equals 1° 36´. They have consulted the seventeenth century military treatise, Treatise on
Armament Technology and Chart of Sea‐Crossing by Fettering Stars to determine the
magnitude of the isba. This sea‐chart preserves some contemporary notations, such as “華蓋五
指”(Cassiopeia, five fingers), “北辰星一指平水” (Pole Star, one finger above horizon).
Whatever the value of the isba, this map uses the isba first to record angles, but also to record
the height of the Pole Star at different locations.
When Yen Dunjie reconsidered these sources, he argued that the zhi equals to 1° 36´, or 1°
+ 36/60 °, and originated from the Islamic world.29 He studied the term isba in several contexts
and used the celestial coordinate system to reconstruct its value. Yen also explained how he
figured out the value for this measurement. At some known latitude confirmed by the altitude
of the Pole Star, one isba is very close to 1° 36’ and one zām is almost equal to 0° 12’.30
In another reconsideration of ancient sources, Zhao Lujun 趙鹿軍 tried to calculate the
magnitude of the isba by examining thirty‐eight locations marked in the sea‐chart preserved in
the Treatise on Armament Technology. From these measurements, Zhao arrived at each isba
having a value of two degrees.31 In contrast to this conclusion, José Manuel Malhão Pereira
drew on experiences on real naval voyages and arrived at a result of an isba being equal to 1°37’
degree.32
One explanation of these differences may lie in the fact that a word can have two
meanings. Although isba is a technical term, it need not have the same magnitude among all
26 Phillips, George 1898, p. 219‐220. 27 Tibbetts , G. R., 1981, p.316. 28 Yan, Dunjie 嚴敦杰, 1966, p. 77‐88. 29 Yan, Dunjie 嚴敦杰, 1966, p. 77‐88. 30 Yan, Dunjie 嚴敦杰, 1966, p. 77‐88. 31 Zhao, Lujun 趙鹿軍;Yan, Xi 楊熺, 1985, p.116. 32 José, Manuel Malhão Pereira, 2003, p.27.
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authors. Different values for a unit of measure are a minor difficulty compared to the different
uses of its fractional unit, the zām. One of the meanings of zām is the part of the circle or
sphere, specificaly one eighth of an isba. These zām were the “octaval minutes” used by
navigators. Another meaning, though, is one eighth of a day. From this meaning, zām came to
mean the distance sailed during a zām. For this reason, sailing for south or north will reduce or
increase the number of isba in the measurement of the Pole Star, so the distance which the ship
has sailed can be related to changes in the measurement of the Pole Star.
Given that the earth’s circumference is about 40,075 kilometer and that a ship sails fast
enough to raise the Pole Star by 1 isba each day, how far does a ship sail in 1 zām? Let the
circumference of the earth be measured as 360°. Thus, 1° is about 111.3 kilometer. Yen Dunjie
reports that 1 isba is equal to 1° 36´, (or 1 + 36/60 °). The equation may be written
1 isba 1° 36´ 1 isba 1° + 36/60° 1 isba 60/60° + 36/60° 1 isba 96/60° 60 isba 96° 60/96 isba 96/96° 5/8 isba 1° 0.625 isba 1° 0.625 isba 111.3 km 1 isba 111.3 km / 0.625 1 isba 178.08 km
But, from the relationship of time measurments, 1 isba is equal to 8 zām which is again equal to
24 hours.If a ship sails north or south for one day, it raises or lowers the Pole Star by 1 isba.33 If
a ship can move the Pole Star 1 isba in 24 hours, how fast is the ship moving?
Speed = Distance / Time
178. 08 km / 24 hours
7.42 km / hour
Since 1 zām equals 3 hours, a ship that travels fast enough to raise the Pole Star one isba in
one day travels roughly 22.26 km over the surface of the ocean in 1 zām. This value agrees very
well with the approximation that a zām is 20 km, an explanation of zām commonly found in
33Tibbetts, G. R. 1981, p.297.
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navigational accounts.34According to this explanation, ship sailing a distance of one isba needs
to sail for a time of eight zām, or in other words, for one day.
Zām not only can be converted into isba but also mean a division of time in Sanskrit.
Here one zām is equal three hours. This measurement of time was used in ancient India.35 The
Indian sailors dialects also has several terms such as wam, bam, tan, bagan, and maaru. Some
of these words seem to be phonetically related to zām. In these uses, one zām indicated a time
equal to three modern hours. In the case of sailing, though, the terms which relate to sailing on
the open‐sea measure time and distances relative to each other.36
On the other hand, the tirfa method demonstrates what the same words actually meant
in Arabic. Tirfa measurements were calculated in zām which had long been used in the Indian
Ocean37 as a measurement of distance sailing. There were eight zām in each day in ancient India.
They separated the twenty‐four hours into eight parts. Each day time and night time has four
zām. It was measured in royal courts also called yamam in Tamil.38In this usage, the zām was
the distance travelled by a ship on a fixed bearing in order to raise its latitude by 1 isba.39 That is,
the zām means a period of time for how long the ship had been sailing. For this reason, if a
navigator sails north and measures the Pole star until it rises by one isba, the time taken was
equal take eight zām (twenty‐four hours). The circumference of Earth is large, though. That is
why even though the isba is not a large division of the instrument, it still indicates the
measurement of an arc. This arc, in turn, can be converted into zām, which is connected with
ideas of time‐measurement.
34 Arunachalam, B. 2008, p.202. 35Arunachalam, B. 2008, p.202. 36 Arunachalam, B. 2008, p.202. 37Tibbetts, G.R. 1981, p.299. 38 Arunachalam, B. 2002, p.14. 39 Tibbetts, G.R. 1981, p.299.
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Figure 4: Diagram which shows the relationship between one isba and 8 zām.
So, how did the zām work with navigation? Ibn Mājid gave examples. Suppose there are
two ships sailing to the northwest. Both ships see the Pole Star to the north by northwest. Both
ships “raise” the Pole Star by one isba, but one ship sails 14 zām and the another sails 16 zām.
Ibn Mājid describes how to find which directions the ships sailed. As Tibbetts elaborates, in
which Ibn Mājid did not explain for zām clearly for navigation. The basic mistake is the example,
there are also two ships, one sailing to the northwest, another sailing to the north–by‐
northwest. After the Pole Star rise one isba, the first north‐bound ship has travelled eight zām
and north‐by‐northwest‐bound ship has travelled 10 zām. However, we can not assume that
the sum of the two short sides of a triangle minimally equals the longest side.
Figure 5: Diagram which relates one possible arrangement of the zām in a triangle. The dimensions of the triangle may vary by wind.
10 zām 8 zām
2 zām
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Actually, when these details are combined with zām and other directions, it can be found
that the hypotenuse of triangle is actually described by the directions on the compass. The
figure below shows the Arabic compass, with the number of zām added to the directions. These
zām indicate how long a ship would have to sail in each of these directions in order to reach the
same distance to the north. These numbers of zām were from Sulaimān who was another
famous navigator and lived later than Ibn Mājid. Very possibly he could have relied on Ibn
Mājid’s idea and used them to navigate the Arabian Sea and the Persian Gulf.40
Thus, since these numbers are a little different, it could be very possible that the different
sailors had different ideas according to their personal or experiences from their navigational
familiar. After all, technical navigational knowledge was transmitted between cultures and
accumulated from several generations.
Figure 6: An Arabic compass‐rose. The arrows in the middle of the compass are very similar to the “wind roses” marked on sea‐charts. As Tibbetts described, directions were also named by zām, and the names actually contained elements of spherical trigonometry which could be used with stars to tell navigators how long to sail in each direction. ( G.R. Tibbetts, 1981, Arabic Navigation In The Indian Ocean Before The Coming Of The Protuguese, London, Royal Asiatic society books, p.297.)
40 Tibbetts, G.R. 1981, p.302.
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Navigationmethods
QiyasQiyas can be assumed to be general navigation methods. The most famous and important
of the qiyas is the technique of using the Pole Star. The Pole Star is like the axis of heaven and
all stars move around this. As we have seen, sailors measured the Pole Star, or when they were
close to the equator, they at least measured the nearby stars. The Pole Star will change its
altitude from the horizon depending on the observer’s location. They may have measured with
their fingers to find the angle between the stars and the horizon. For this reason, sailors used
the isba as the unit for measuring the angle between the Pole Star and horizon. The arc which
measures the elevation of the pole from the horizon, thus expresses “degree of latitude” or
“degree of longitude”. This measurement is not expressed as a degree, but simply as the
distance to the equator or the meridian.
However, a complete knowledge of this qiyas concerning the Pole Star involves other
elements of astronomical knowledge. For example, the stars near the Pole Star are also
important. Actually, there is no star at the North Pole. Thus, sailors needed to know that jah is
the Arabic name of the star which stands near the North Pole and jady is the name of Capricorn.
(When both of them rise at same time, it is a good omen in Arab world.) This empty area can be
separated into two parts. One empty part is called “eastern” and another empty part is called
“western.” These directions may be indicated by an astrolabe or lodestone. However, due to
the precession, the Pole Star is very close the real North Pole, and that is why the degree
between horizon and Pole Star is almost the latitude on geography.41
There are three conditions that make the qiyas method useful. The first condition is
weather. In order to take these measurements, a sailor would have to hold an instrument as
steady as possible with hands and teeth. These instruments cannot be used well in strong winds
and strong waves.
Along with the qiyas of measuring the Pole Star, Arabic sailors used the 32 rhumbs with
tirfa, zām, and qiyas. The qiyas of measuring the altitude of a star as a guide to latitude was
41 Yan, Dunjie 嚴敦杰, 1966, p.77‐88.
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combined with the compass rose and the division of the ship into 32 parts. Also, the boat was
imagined like the needle of a big compass on the open sea and the rhumbs were marked by
constellations. For example, Farqadan (two stars near Ursa Minor) stood opposite the star
Achernar (α Eridani). These stars represent the bow of ship and poop, respectively, but they are
also used to mark directions.
The second method of qiyas relied on Farqadan and Sulbar. The two stars of Farqadan rises
at dawn with Libra (Zubanan) and Sulbar is the same star as Achernar. In the fettering method,
sailors preferred to use al‐shiʿ'rā (الشِّعرى, Sirius) and al‐waqui (Vega), because Sirius is brighter
and clearer to observe. According to Tibbetts, Arab sailors used the Pole Star as a standard,
because Sirius and Vega stand at almost the same altitude of heaven for these three stars to
form an isosceles triangle.
Europeans calculated the “raising of the Pole.” This method is similar to the tirfa method of
Persian origin. This method considered the distance travelled by a ship and calculated the time
in terms of zām which had been used for a long time in the Indian Ocean. One zām equal three
hours, eight zām equal twenty‐four modern hours and eight zām is one isba. Until the fifteenth
and sixteenth century, though, zām were also an angular measure for navigators, which meant
the surface of the sea and was an arc unit in navigation.
‐ 25 ‐
Figure 7: Diagram of Finding Latitude. When people stand at different laitutides and observe the same star, the star appears at different relative positions. In this example, the angle between the Pole star and the horizon is different for observers at A and B.
FetteringThere were other methods of using stars for qiyas measurements. These were used
especially when the Pole Star could not be observed on cloudy days. For example, in the
“fettering” method, sailors used familiar stars. Each particular star or constellation had links to
other stars or constellations. By comparing the two observations, the sailors could determine
the time. Stars observers also used this simple skill to memorize stars positions. In different
times and places, different stars were used. Sometimes they used Achernar with the rising of
Sirius and other times they used Achernar with the setting of Vega.
Unfortunately, there is no system which covers the whole range of possibilities. As noted
above, sometimes sailors used Vega and sometimes they used Sirius. In the sky, Vega and Sirius
are at almost the same altitude. If one star can be observed, the observation of the other one
will also probably be accurate. Ibn Mājid prefered to use Sirius as his standard when he sailed
near Oman and the Persian Gulf.
Moreover, the technique of fettering also has a similar meaning in Chinese. The word for
fettering may be translated as qian 牽 in Chinese. This word also means “to hold up”, or “to tie
‐ 26 ‐
together,” like the combination of stars on starry night. This word is connected with the qianxin
ban 牽 星 板 , the so‐called “star‐fettering boards” which are mentioned as navigation
instruments in Chinese sources. In addition, it is could be possible that this device worked
according to an underlying theory which was brought from the Islamic world.
Abdāl
Another method presented in accounts of measurements of latitude is the abdāl. This
method is used for two stars when they were at the same altitude in the sky. For example, Vega
and Capella are two bright stars which stand at a suitable position.
Figure 8: Diagram for Finding the Meridian. When two bright stars stand on the same altitude, sailors could imagine the trangle for these two stars and make the meridian line. In this example, Vega and Capella mark the meridian. As a result, it is easy to observe the passage of the bright star and understand time.
These two bright stars are at almost same altitude. That is why abdāl relationships were
related to the meridian. Sailors used these stars which stood at the same altitude to imagine the
meridian line between these two stars. Sailors could tell time according to which star was on
the meridian or by which lunar mansion crossed this line. For this reason, the lunar mansions
also become very important in the knowledge of Arab navigation technology.
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NavigationalMiscellanyOther knowledge was also useful to navigation. Much of this information was not
astronomical. This general knowledge related geography and meteorology (weather patterns)
to navigation.
The tides, winds, landmarks, water‐coloration and other geographic features all together
were called ishārat. For sailors, these were all the basic things they needed to know, such as the
coastline, the sand colors in different depths of the levels of the sea. The ishārat also included
familiar situations of the appearance of the shore when they were close land and what features
could first be seen on the horizon. All the descriptions of Red Sea include some of these
landmarks and features. For example, the environment of the atolls near the Maldives are often
described in detail. Moreover, the sea‐snake was listed as a common observation off the Indian
coast when coming from Arabia. These descriptions even extend to cuttle fish and specific types
of birds, like umm ṣanānī, the munjī and the kuraik which were easily identifiable.
Another important element in Arab navigation was the use of bearings, which they called
majra.42 The compass was used to know the direction and the compass needle identified the
direction on the compass card. This card used rhumbs. When Europeans crossed the Indian
Ocean, they used a magnetic compass needle or lodestone or some other compass‐like device,
combined with the rhumb to avoid getting lost on the open sea. Arabs named these directions
with reference to the image of the boat on open sea. In this picture, the boat was like a big
compass needle and it was separated into 32 parts.
Crossing the open‐sea was the most important and necessary situation for using lunar
mansion as a navigational skill. For sailors, sailing along the coastline was the best and safest
way to avoid getting lost. However, when navigational technology developed and people want
to save time, sailing on the open sea became a progressive choice.
42 Tibbetts, G. R. 1981, p.290.
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Monsoon
MonsoonsoftheArabianSeaThe season for leaving from Arabia to India was determined by the southwest monsoon.
The southeast monsoon began in March on the eastern shores of Africa. This wind normally
blew eastward until June. This wind drove boats to reach the coast of Gujarat until late May or
early June.43
For the return trip, navigators relied on the Northeast monsoon. This monsoon blows
from mainland India and carries no rain. This monsoon began in early October in the Sind
province of Pakistan and reached Ceylon. This monsoon blew until March in the next year.
Sailors who sailed the Arabian Sea were familiar with this monsoon as well.44 Together, the two
monsoons made a “round trip” which was dependant on the calendar and the sailor’s country
of departure.
MonsoonsoftheIndianOceanFor the navigators who sailed the Indian Ocean, the winds also represented the directions.
For Indian navigators, there were some mnemonic devices which associated the technical terms
for the winds with the areas which lay in those directions. Sailors were familiar with the
monsoons and their directions. For example, they knew the strong monsoon from the south‐
west drove ships to Malabar and Lakshadweep, and the name of this wind of meant “cloud” in
Tamil Nadu.45
In addition, some winds were even named by the morning rising and evening setting of
specific stars from horizon. For example, the Arab katru (Arab wind) was named after the
setting of the star Arab (Antares). Likewise, the Sothi katru (Sothi wind) was named after the
rising of the star Swati (Arctrus). Moreover, some winds were associated with some specific
areas, like the ela‐katru which meant “the Ceylon wind” in southern Tamil Nadu and the
northwesterly Poysachi vara, which meant “Persian wind” in Konkan. 46
43 Tibbetts, G. R. 1981, p.364‐367. 44 Tibbetts, G.R. 1981, p.371. 45 Arunachalam, B. 2009, p.206. 46Arunachalam, B. 2009, p.206.
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Figure 9: Wind‐Compasses used around India.Different regions of India referred to the directions by different wind names. (source: B. Arunachalam, 2009, p.19. )
Wind is an important condition for navigation, not only to power the ship but also to tell
sailors the direction. The monsoon is the main power to cross the open‐sea but in many specific
places, the winds are different with respect to information for navigation. Thus, according to
different harbor, Arunachalam reported each direction named by the wind. When a full set of
eight directions can be found, these are another type of compass and can be called “wind
compasses”.
We know this information not only from Chinese sources, but also from Islamic material.
They called the southwest monsoon from Arabia to India was the Rih‐al‐Kaw or the Rih al‐
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Dabur.47 The southwest monsoon began in March at the east African coast and grew strong and
spread until June to arrive at the Indian peninsula. On the other side, the Arabic name is for the
northeast monsoon Rih Azyab or the Rih al‐Saba. This monsoon sprang from the mainland with
no rain and began in early October in Bengal in winter. When the season was coming, the
monsoon could change, and that mean it was time to sail. And that is what the Swahili called rih
al‐qila ain for “wind of two sails”.
There are some empiprical knowledge about sailing in Indian Ocean. When sailors departed
from China, it was hard to predict the exact day or time of wind change from north to Northeast
wind. Normally they departed before May, as experience. If they departed later than the tenth
of June, on they could not arrive at Hormuz on this voyage.48 On the other side, from Omen or
Yemen on the Arabic peninsula back to India, boats can almost sail all year, especially from May
to July, when the Southwest wind was strong in the summer season. In this situation, sailors
went from Red Sea back to India, from Ceylon to Sumatra. Due to the Northeast wind, it was
also hard to sail when departing in November.
The monsoon method was used well and it can also be seen in this record on maps. There
are two figures that point out how the monsoon important on was this sea route. Moreover, it
also marked the wind direction and seasons. This is a map by Herman Moll (1654‐1732), who
was an important geographer in England in seventeenth century. Although this map was
published in eighteenth century, the information of monsoon shows us sailor still relied on this
to navigate. This map contained the Indian Ocean, the monsoon direction, and eight‐seven
newly discovered island.49
To understand wind represents a huge intellectual endeavor which drew from a wide range
of sources. However, when the voyage is considered holistically, the monsoon winds were still
important even until the eighteenth century.
47 Tibbetts, G. R. 1981, p.368. 48 Tibbetts, G. R. 1981, p.372. 49 According to the introduction of exhibition “Geo|Graphic: Celebrating Maps and their Stories,” held at the National Library Board, in Singapore.
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Figure 10: Map of Asia Herman Moll (1715). This figure was taken from the exhibition “Geo|Graphic: Celebrating Maps and their Stories,” held at the National Library Board, in Singapore. This map marks the wind direction by the arrows and also describes them with a month. The monsoon corresponds with the departure and return season. The Northeast wind is in the winter and the Southwest wind is in the summer in the Southeastern area.
Figure 11: Map of Asia Herman Moll (1715). This figure is also taken from the exhibition, “Geo|Graphic: Celebrating Maps and their Stories,” held at the National Library Board, Singapore. The monsoon winds follow the rule that the Northeast wind is in the winter and the Southwest wind is in the summer. The regularity of these winds helps navigators cross the Arabic Sea from India.
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LunarMansions:The lunar mansions were a kind of ancient technology of observation. There were two
methods to account for its origins. In the first method, ancient astronomers observed the circle
of moon and its relationship to the ecliptic. Then they separated the circle into the stations
based on the average number of days the moon took to pass by all the stars. By the other
account, the method developed from observing the bright stars on the horizon during the dawn
and evening. In the course of the average lunar month, the astronomers checked which lunar
mansions the moon occupied before sunrise. The distance the moon moved every day of the
lunar month was identified as a lunar mansion.
Before the Islamic Empire grew up, the Bedouin had used this system and called it anwā’
Moreover, some Indian systems of astronomy from pre‐Islamic dates also used Lunar Mansions.
For some specific areas in India, astronomers chose this method to the observe pathway of the
moon. Thus, when Muslims found this Indian knowledge, they adopted