For the calculation to be accurate, both the observer in Nanjing and the navigator in the Indian Ocean must be looking due north at Polaris. If they wish to use the second method to calculate longitude, both must have precisely the same midnight. They do this as follows: First they use a vertical stick to measure the sun’s shadow. When the shadow is shortest, the sun is at its maximum height at midday and is due south. Both observers build a trench running due north-south, a trench that can be flooded to see the reflection of Polaris at night and emptied of water to measure the sun’s shadow at midday.
The sun’s shadow when at its shortest can be measured on the trench. To get the precise second, the shadow is sharpened by employing a pinhole camera atop a pole called a gnomon (described on the website). By using identical gnomons and a standardized pinhole camera, the observers in Nanjing and the Indian Ocean can each determine the same due south/north and the same instant when the sun is at its highest—that is, midday. Our experiments described on the 1434 website have shown that they can calculate this to within two seconds. They can now use a standardized clock to calculate midnight, twelve hours after midday. The 1434 website explains how this Chinese clock worked and how, in Zheng’s era, refinements were built to compensate for different temperatures and air pressures, which would otherwise have affected the number of drips coming out of the clock. Thus time was accurate to within two seconds.
Using the water clock, the observer in Nanjing and the observer in the Indian Ocean establish the same midnight. After sunset the trench is flooded and two poles are placed on either side of the trench; a line is suspended horizontally between the poles. Another line is hung vertically so the observer can see the reflection of the vertical string in the water of the trench in line with Polaris. At the instant of midnight, the navigator in the Indian Ocean looks at the star in line with Polaris reflected in the water, which is in line with the string. (In our example, on day 141 this star is Betelgeuse.) His tables for day 141 say that in Nanjing the star is Aldebaran. From that, he can determine his longitude. According to Robert Cribbs, the method is accurate to within two seconds, which amounts to a maximum error of three degrees in longitude, negligible for mapping the world.
This method requires the navigator to be on land. However, Professor Cribbs has also developed a method of determining longitude at sea by using the equation of time of the moon and the angular distance between the moon and a selected star. To deploy this method (see 1434 website) some calculus is required to establish the future position of the moon for the 1,461-day cycle. By 1280, Guo Shoujing had established a system very similar to calculus. The results appeared in his tables and calendar, which were adopted by the Ming in 1384. Consequently, they were available to Zheng He’s fleets, as were tables of declination of the sun.
Thanks to Tai Peng Wang, who brought the matter to my attention, and to the work of Xi Feilong, Yang Xi, and Tang Xiren, who have recently discovered the star maps of Zheng He’s voyages, we know which stars Zheng He’s fleet actually used to determine latitude and longitude on their passage to India. They sailed with the monsoon winds, starting across the Indian Ocean from the northwest tip of Sumatra at Pulau Rondo, now called Banda Atjeh, on October 10, 1432, determining latitude and longitude as follows: “Gauging the vertical positions of the given stars above the horizon in the east, west, north and south, they reached Sri Lanka.” Using Vega, Sagittarius, Gemini, and Poseidon, they arrived at Calicut (11° N, 76° E) on December 10. See the TPW paper “Zheng He’s delegation to the Papal Court at Florence” on the 1434 website.
Finally, how accurate were Zheng He’s navigators? Two answers produce the same result: their measurement of declination at 22°23'30'' (correct to within two miles) and the accuracy of the eye, which can be judged to within a quarter of a degree—the full moon appears large but its diameter is under half a degree (thirty miles).
It is my submission that Zheng He’s navigators were able to calculate latitude to within half a degree, or thirty miles, and longitude to within two seconds, or three degrees. When the fleets arrived in Venice and Florence, their methods of calculating latitude and longitude were transferred to Europeans. In due course, Columbus and Vespucci used them to reach the New World.
5
VOYAGE TO THE RED SEA
On January 19, 1431, the fleets left Nanjing, China. They invariably sailed in January because of the free power provided by the monsoons, which to this day determine sailing patterns from China across the Indian Ocean to India and Africa.1
Monsoons are caused by the difference in temperature between the massive Himalayan plateau and the sea. In summer the Asian landmass becomes hotter than the ocean, sucking winds and water vapor off the sea. In April the southwest monsoon is heralded by westerly winds in the Indian Ocean. By May the southwest monsoon hits Indochina to reach its peak and constancy in July, by which time winds reach thirty knots in the South China Sea. By now India is flooded with monsoon rain. During September the temperature drops, and by November, when the Himalayas have become bitterly cold, air is drawn off the mountains by the warmer seas.
The northeast monsoon starts in late December, after which the wind gradually abates until April, when the cycle begins again. Ships sailing between China, India, and Africa took advantage of these monsoons to sail before the wind, returning on the next monsoon to their respective countries. They awaited the change of monsoon in some sheltered harbor. For example, in Southeast Asia, by the time Indian ships had arrived in the Malacca Strait with the southwest monsoon winds, Chinese junks had not yet departed their home ports. By the time the Chinese arrived, the Indian ships were gone. Hence the need for harbors around the Indian Ocean where goods could be stored from one monsoon season to the next. The Chinese and Arabs built entrepôt ports in Southeast Asia and around the Indian Ocean where goods were warehoused en route to their final destinations.
Monsoons were so predictable—and important—that they were incorporated into Arab calendars, which illustrated the highly synchronized system of regular shipping between Egypt, East Africa, India, and the Gulf. For example, one such calendar describes day 68 (March 16): “End of sailing of Indian ships from India to Aden: no-one ventures after this day.” (See research of Tai Peng Wang in notes).
Zheng He’s fleets took advantage of this Islamic navigational calendar, joining the regular schedule of shipping. As the historian Paul Lunde points out in “The Navigator Ahmad Ibn Majid,” on day 100 (April 15) the last fleet from India was scheduled to arrive in Aden. The departure from Egypt of the first ships of the convoy, owned by the Karimi merchants, was timed so the convoy’s arrival coincided with the Indians’. Four months later, on August 14 (day 220), the last ships from Egypt arrived in Aden. Six days later, ships from Sri Lanka and Coramandel set out on their voyage home. The last departure from Aden, powered by the monsoon, was on day 250 (September 13).
In Zheng He’s era, ocean trade was dominated by the Arabs and Chinese. The Chinese made goods that the rest of the world craved—principally, porcelain and silk. Chinese junks carried these valuable cargoes to Malacca, India, and Cairo. Malacca was virtually a Chinese colony. In Calicut, on the Malabar Coast of India, Chinese and Arab traders met in equal numbers.
Relations between the Chinese and Arabs had been friendly for centuries. In Cairo the Chinese were an established minority. Likewise, there was a substantial Arab quarter in the Chinese port of Quanzhou. Many Arab navigators and interpreters joined Zheng He’s fleets.
In every respect—numbers, ship construction, cargo capacity, range, defense, communications, supplies, the ability to navigate in the trackless oceans, and the repair and maintenance of ships at sea for months on end—the Chinese were centuries ahead of Europe. The most powerful fleet after China’s belonged to Venice, which possessed around three hundred galleys—fast, light, shallow ships rowed by oarsmen. Venetian galleys, the largest of which carried around fifty tons of cargo, were suitable for calm summer days in the Mediterranean
—but not for anything like the travails of the Chinese fleets.
Zheng He’s treasure ships were oceangoing monsters, capable of sailing through storms across the oceans of the world for weeks at a time. Carrying more than a thousand tons of cargo, they could reach Malacca in five weeks, the Strait of Hormuz in twelve. Staterooms were provided for ambassadors and their staffs returning to India, the Persian Gulf, and Africa. More than 180 medical officers were on the admiral’s staff; each ship had a medical officer for every 150 men, and they took on sufficient citrus and coconuts to protect them from scurvy for two months. Caulkers, sailmakers, anchor repairers, scaffolders, carpenters, and specialists in tung oil application maintained the ships during the voyage. In addition, the ships carried interpreters who could communicate with rulers in India, Africa, and Europe—in Hindi, Swahili, Arabic, and Romance languages. As with all Chinese expeditions, astrologists and geomancers accompanied the fleets.
While Venetian galleys were primarily protected by archers, Chinese ships were armed with gunpowder weapons—bombards, fragmentation mortars, cannons, flaming arrows, even shells that sprayed excrement over their targets. With these awesome weapons, Admiral Zheng He would have no difficulty destroying pirate fleets. A contest between a Chinese fleet and a rival navy would resemble that between a shark and a minnow. In his final voyage, Zheng He commanded fleets more than ten times the size of Nelson’s at Trafalgar.2
However, there were two major distinctions between this final voyage and previous trips. First, huge improvements in cartography, navigation techniques, and ship construction made the voyages safer and their destinations more likely to be reached. Second, the principal purpose of this voyage was to present foreign rulers with the Xuan De calendar and with charts and navigational aids to enable foreign rulers to return tribute to China. When Zheng He’s junks returned in 1434, the Xuan De emperor, Zhu Zhanji, was able to claim that “ten thousand countries [are] our guests.”3 In the years immediately thereafter, a dozen countries paid tribute to the emperor, including an enormous delegation from Egypt.
Thanks to the research of Tai Peng Wang, we are able to follow the precise route of Zheng He’s and Hong Bao’s fleets to Calicut. Xi Feilong, Yang Xi, and Tang Xiren, in their recent discovery and analysis of The Charts of Zheng He’s Voyages, have reproduced Zheng He’s route and identified the specific stars his navigators used to determine latitude and longitude on the way to India.
Sailing with the monsoons across the Indian Ocean, their point of departure on October 10, 1432, was Pulau Rondo (Banda Atjeh) on the northwest tip of Sumatra (6°04' N, 95°07' E). Zheng He’s book of charts describes how by “gauging the vertical positions of the given stars above the horizon in the east, west, north, and south (they) reached Sri Lanka.”
The choice of stars (more accurately star groups—some contain multiple and binary stars) used by Zheng He’s navigators for their Indian Ocean crossing at first appears baffling. The right ascensions (“longitude in the heavens”) are Poseidon, twenty hours, Vega, eighteen hours, Sagittarius, nineteen hours, and Gemini, seven hours. So the positions obtained from their measurements would correspond to their right ascension and the distances from the stars illustrated by the lines CD, EF, GH, and IJ on Fig 6 on our website. That is, an approximate line of 015/195 (seven hours/nineteen hours). Why do all the chosen stars have approximately the same right ascensions? Why not select different stars from different parts of the heavens?
The answer becomes clear when Polaris is considered. Polaris is at 90° elevation at the North Pole and 0° at the equator. Thus the height of Polaris in the sky (altitude) equals latitude—the line AB, Fig 6 on our website. By measuring Polaris’s height, a navigator could ascertain his latitude. The best stars to determine longitude would be at right angles to Polaris, that is, stars with right ascensions of 90 and 270 degrees (six and eighteen hours).
This discovery of Tai Peng Wang and his colleagues enables us to refine how Zheng He’s sailors determined latitude and longitude. For latitude, they used the sun at midday (meridian passage) and Polaris by night in the north. For longitude, they used those stars in the ephemeris tables that had right ascensions nearest six or eighteen hours or, alternatively, the moon. (I was a submarine navigator for four years and never thought of such an ingenious solution. One would have needed only two looks through the periscope—when one was at most risk—one at Polaris another at Pollux.)
Wang Jinghong, another admiral, would lead his fleet to the Persian Gulf.
In this chapter, we describe the passage of Zheng He and Hong Bao, then follow the voyage of a much smaller detachment from Hong Bao’s fleet, which sailed up the Red Sea to Cairo and the Mediterranean—following in the wake of Zheng He’s 1408 voyage to the Mediterranean.
On November 18, 1432, when the fleets were south of Sri Lanka, Zheng He ordered Hong Bao to lead the fleet to Calicut, their next port of call. A commander-in-chief does not order one of his flag officers to lead the fleet into harbor if he himself intends to be present. This means that Zheng He was detaching part of his fleet under the command of Hong Bao.4
We know from the charts of Zheng He’s voyages that Hong Bao left Calicut for Dandi Bandar farther up the coast (16° N, 73° E), crossing the Arabian Sea on a course of approximately 330 to make landfall at Jebel Khamish (22°25' N, 59°27' E). After a few days he pushed on to Bandar ‘Abbas, arriving on January 16, 1433. Hong Bao’s fleets returned to Calicut on March 25 and sailed for China on April 9, reporting there the sad news that Zheng He had “passed away.”
How did Hong Bao know that Zheng He had passed away? After his order to Hong Bao, Zheng He seems to have vanished. In my view, for reasons to be described in a later book, after detaching Hong Bao, Zheng He sailed for Africa and North America, settling near what is now Asheville, North Carolina, where he died.
Ma Huan, the historian aboard Zheng He’s fleet,5 describes Calicut in detail. Almost a tenth of Ma Huan’s book is devoted to this city-state, which had become a very important forward base for Zheng He’s fleets. Ma Huan, a Muslim, was delighted to find there were more than twenty mosques for a Muslim population of thirty thousand. He gives a detailed account of how trade was conducted between representatives of the treasure fleet and local merchants and brokers. After negotiations, all parties would clasp hands and swear that the agreed prices would never be repudiated.
These fascinating accounts are mirrored in those of Niccolò da Conti, who had reached Calicut in 1419. As Richard Hall points out in Empires of the Monsoon, Ma Huan and Niccolò da Conti’s descriptions are almost the same word for word,6 not least in the descriptions of the Indian test for guilt (the accused’s finger was dipped in boiling oil; if the finger was burned, it signified guilt).
Niccolò accurately describes construction of the Chinese junks, so I am confident that he boarded one of Zheng He’s junks in 1421, which would have given him the ideal opportunity to acquire a map. Just such a map, as I will describe later, turned up in Venice before 1428, and a copy can be seen today in the Doges’ Palace. (Although Niccolò da Conti may not have returned to Venice until 1434, in the 1420s he had entrusted his mail to a friend, Piero Tafur, who took it to Venice on his behalf.)
On his 1432 voyage, Hong Bao did not stay long in Calicut. When he arrived, Calicut merchants were about to leave for Tianfang (Egypt) in their own fleet. Hong Bao seized the opportunity, detaching two junks and seven senior officers for a trade delegation laden with silks and porcelains, which joined the Calicut fleet.7
The story is taken up by Ibn Tagri Birdi, the celebrated Egyptian historian, in his history of Egypt, Al Nujun AzZahira Fi Mulek Misr Wal Kahira, who writes in 1432:
A report came from Mecca, the honoured, that a number of junks had come from China to the seaports of India and that two of them had anchored in the port of Aden, that their goods, chinaware, silks, musk and the like were not disposed of there because of the disorders of the State of Yemen…. The Sultan wrote to them to let them come to Jed
da and to show them honour.8
As Tai Peng Wang points out, there were very good reasons why the Chinese envoys should rush to Mecca—Zheng He and many of his eunuch captains were Muslims. The Ming envoys had been ordered by the emperor to announce the imperial edict of the Xuan De emperor to the kingdoms of Maijia (Mecca), Qian Lida (Baghdad), Wusili (Cairo), Mulanpi Kingdom (Morocco), and Lumi (the Papal States), to inform them that they were all his subjects.
According to the Ming Shi-lu (the official Ming history), Egypt and Morocco were among those foreign countries that in Zhu Di’s reign (1403–1424) had already received the Chinese imperial edict and gifts (the 1408 visit—Ming Shi-lu) but had failed by 1430 to return tribute to China. However, the Ming Shi-lu noted that the Papal States and Baghdad were among the foreign countries that had already sent tribute to Ming China during the reign of the emperor Zhu Di.
In 1432, Mecca was part of the Mamluk kingdom of Egypt. The Mamluks ruled by far the richest country in the Western world at that time; Cairo was the world’s largest port outside China. The ships that Hong Bao had dispatched to Mecca had also been ordered to Cairo,9 which lay farther up the Red Sea through the Red Sea–Nile canal. Evidence of the Chinese visit to Cairo comes from the description of the Pyramids on the 1418 Chinese map and in other contemporary Chinese records.
We get a vivid description of earlier Chinese junks from Ibn Battutah who wrote of the immense size of the ships, their petroleum weapons, the luxurious quarters for merchants, and the poor slave girls.
Descriptions of the Chinese Vessels
The Chinese vessels are of three kinds: large ships called junks, middle-sized ones called zaws, and smaller ones called kakams. The large ships have anything from twelve down to three sails which are made of bamboo rods plaited like mats. They are never lowered, but they turn them according to the direction of the wind; at anchor they are left floating in the wind. A ship carries a complement of a thousand men, six hundred of whom are sailors and four hundred men-at-arms, including archers, men with shields and arbalists, that is, men who throw naphtha. Each large vessel is accompanied by three smaller ones, the half, the third, and the quarter. These vessels are built only in the town of Zaitun in China or in Sin Kalan which is Sin al Sin [Canton]…. At the side of these baulks are their oars, which are as large as masts, ten or fifteen men joining together to work each of them, and they row standing on their feet. In the vessel they build four decks, [with] cabins, suites and salons for merchants. A set of rooms has several rooms and a latrine: it can be locked by its occupant, and he can take along with him slave girls and wives…. Some of the Chinese own large numbers of ships on which their factors are sent to foreign countries. There are no people in the world wealthier than the Chinese.10
1434 Page 5