Friday, May 12, 2006

Magnetic Compass and Navigation (Glossary)

Joseph Needham suggested that the magnetic compass, portolan chart, sandglass and tavalo di marteloio were part of a package that appeared rather suddenly in Europe and might have owned much to Chinese developments.

The whole set of techniques gave rise to the practice of dead reckoning and "quantitative navigation" that made the European age of exploration possible.

China indeed has a long history of knowledge of the magnetic compass. As early as the 4th century BCE, there is mention of use of a south-pointing compass for use in long overland voyages. A magnetized ladle was used as a geomancy compass starting in the Qin dynasty.

Adelard of Bath in 1117 was the first European to note that the lodestone pointed in a certain direction. In 1190, Alexander Neckham mentions magnetic needles used for marine navigation.

Muhammad al-Awfi writes of a fish-shaped magnetic compass in 1232 and 10 years later Bailak al-Qabajagi states that mariners in the Indian Ocean used an iron leaf shaped like a fish and rubbed with a magnet to find direction.

The fish shape of the compass mentioned in Muslim works is important because a description of a floating fish compass occurs in Chinese texts dating back to 1027.

According to the Shih Lin Kuang Chi dated sometime between 1100 and 1250, it is said that the floating fish compass was the invention of the Daoist Immortals:

They (the magicians) cut a piece of wood into the shape of a fish, as big as one's thumb, and make a hole in the belly, into which they neatly fit a piece of lodestone, filling up the cavity with wax. Into this wax a needle bent like a hook is fixed. Then when the fish is put in the water it will of its nature point to the south, and if it is moved with the finger it will return again to its original poistion

(translation by Colin A. Ronan, The Shorter Science and Civilisation in China)

While I have written previously that the earliest Austronesian navigation did not require the compass, the device was nonetheless known to Southeast Asian mariners when the first Europeans arrived at the start of the colonial period.

Even when ages-old techniques were still used by most mariners in the region, there was also evidence of at least some use and knowledge of more modern techniques:

Ludovico de Barthema mentions his East Indian pilot to Java in 1505, who used a compass and chart with coordinates:

The captain of the said ship carried the compass with the magnet after our manner, and had a chart which was all marked with lines, perpendicular and across.

Alfonso de Albuquerque in 1512 describes a sophisticated chart he had acquired in Southeast Asia in a letter to King Manuel of Portugal:

...a large map of a Javanese pilot, containing the Cape of Good Hope, Portugal, and the Land of Brazil, the Red Sea and the Sea of Persia, the Clove Islands, the navigation of the Chinese...It seems to me, Sir, that this was the best thing I have ever seen.

According to Albuquerque's account, Southeast Asian navigators already had ample knowledge of world geography at this time and were able to portray such knowledge on map charts.

As mentioned previously in this blog, the earliest advances in map-making in Europe came with the appearance of the portolan chart. This chart in many ways resembled the star and wind compasses used by Austronesian navigators.

With all respects to Needham, the Chinese and European systems were not likely the first examples of "quantitative navigation." They may have been the first to use modern mathematical techniques, but ancient Austronesian navigation was also quantitative techniques.

Journeys to any destination were represented in time-distance units. In this blog, we have referred to these with the Micronesian term etak.

However, this quantity did not need to be divided as in the other systems. Instead, the navigator dynamically adjusts the distance covered by an etak through mental imagery. An etak one day may mean 20 miles and the next day 100 miles. But numerical processes are not at work here so much as a mental shortening or lengthening of the etak.

Such a system might be difficult to transmit to someone in a totally different cultural milieu. However, the general principle of time and distance is the same.

The use of the sandglass allowed the day to be divided into watches. At each watch, the sandglass was turned upside down with an accompanying chant by the watch-person.

This system worked for mathematical computations especially with the newly-popular Indo-Arabic numerals.

Likewise, the traditional Austronesian navigator corrected course deviations using dynamic mental imagery. In Europe, they used instead the tavola di marteloio or traverse tables.

Again, it would be difficult to transmit the Austronesian system to one not raised in the same cultural background. What is accomplished with right-angled trigonometry on the one hand, is handled totally with mental images, on the other.

Needham believed the sandglass may have arose from the many advances in clock technology that evolved in China. It is worth noting though that one particular time-keeping device bore a unique resemblance to the floating fish compass used in the Indian Ocean.

The sinking bowl clepsydra was found in Southeast Asia in the form of coconut shells with holes punched in the bottom. These devices are still used by fisherman in Insular Southeast Asia.

Although no accounts of this device being used in navigation exist, both this "water clock" and the floating fish compass share the quality of being stabilized by flotation. Thus both were useful on ships.

Paul Kekai Manansala


Needham, Joseph, Science and Civilisation in China, Cambridge University Press, 1971.

Suarez, Thomas, Early Mapping pf Southeast Asia, Tuttle Publishing, 1999.