Page 38 - Art In The Age Of Exploration (Great Section on Chinese Art Ming Dynasty)

There are thirteenth-century Arab texts that observatory. There, it is said, he resolved all the because of unfavorable currents and winds.
refer to the magnetic needle, and it is therefore problems posed by the navigation of the Atlantic. Since it was not easy to overcome these obsta-
very probable that it reached Europe through Although the idea of the "School of Sagres" cles, even when they used ships such as caravels
the Islamic world. is widely accepted, it must be a fallacy for that were able to sail close to the wind, the
Whatever the history of the magnetic needle several reasons. First, neither Prince Henry nor pilots tried out new ways of dealing with them.
itself, the rhumb-lines mentioned in the porto- any European, Arab, or Jewish scholar could They would sail out into the Atlantic until, at
lans and later represented graphically on the foresee the geophysical conditions that would about the latitude of the Azores, they encoun-
nautical charts were magnetic and not geograph- be encountered in the Atlantic and find ade- tered winds that would take them home to
ical. The phenomenon later known as magnetic quate solutions for them in advance. Second, Portugal. This maneuver, which took more
declination (that is, the angular deviation of the there is no evidence of any such group of time the farther south the point of departure
compass needle in relation to the meridian line, scholars having been assembled, except for Jaime was, meant that for several weeks, sometimes
which changes from place to place) was then of Majorca, who was simply a cartographer, the for up to about two months, the ships had to
unknown, and observers believed that the line son of Abraham Cresques (see cat. i). More- navigate in open sea without any land as a point
indicated by the compass needle was identical to over, it would not have been possible to set up a of reference. The pilots therefore needed to
the geographic one. This is proved irrefutably meteorological observatory at Sagres, as the establish their approximate location so that
by the nautical charts themselves, since they science itself did not exist in the fifteenth cen- they could proceed with some security, a pro-
always distort, for example, the shape of the tury. Furthermore, we know that Prince Henry cess that led to increasingly more effective
Mediterranean basin, because the magnetic did not spend much time in Sagres until the last navigation techniques.
declination varies from place to place. It is two years of his life, when decisive progress in Initially, the navigator would estimate his
noteworthy, nonetheless, that the nautical charts the new techniques of navigation had already north-south distance from a place of reference
of the Mediterranean remained unaltered until been made as a response to the demands of based on the difference in altitude of the pole-
the eighteenth century; this is to be expected, Atlantic navigation. Until 1458 he visited Sagres star—or any other easily identifiable star—on
because recent studies of magnetism in earlier only occasionally and did not stay long enough the transit of the same meridian. The result
periods show that the degree of magnetic decli- to direct a school. The idea of the "School of would be the number of leagues, counted on a
nation itself was practically unchanged for about Sagres," which is as fallacious as it is famous, meridian, that separated the parallel of the
four centuries. goes together with the idea that advanced stud- observer's location from the parallel passing
This, then, was the knowledge and equip- ies in astronomy were necessary to develop a through the place of reference. For example, if
ment to which a pilot in the early fifteenth new manner of navigation, as well as the idea the navigator took as his point of reference the
century had access. Alfonso X of Castile that the Prince took a great personal interest in parallel of latitude passing through Lisbon,
(r. 1252-1284), in his Partidas (Ships' Crews), these studies. The romantic historian Oliveira where the upper meridian passage of the pole-
required of the pilot some additional knowl- Martins even hypothesized that he had read the star was at the astronomical altitude of 42°, and
edge, such as an understanding of maritime works of the German astronomers Peuerbach at sea he measured the equivalent transit of the
currents. He did not refer to the traverse board, and Regiomontanus, which were not in print polestar at 35°, he could conclude that the
which allows a pilot to return to the straight until 1460, the year Prince Henry died! parallel of his location was separated from that
course if he has had to leave it because of winds, While extremely important, the fifteenth- of Lisbon by 7° (that is, the meridian distance
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currents or natural obstacles such as islands or century change in the art of navigation did not between these two parallels was 7 times 16 / 3
shoals. Its invention has been attributed, with- require specialized scientific training, and the leagues, the value then used for the unit of one
out sufficient foundation, to Ramon Llull of little astronomy that was necessary was so degree of latitude).
Majorca. If it was Llull's contribution to the art simple that pilots were able to find the solutions This idea must have originated through the
of navigation of his time, it is the only one he by their own means. When this was not possi- influence of Joannes de Sacrobosco's thirteenth-
made. The Aragonese did have a school of ble, they consulted astrologers, who had no century treatise Da Esfera (The Sphere). This
cartography partly under the influence of difficulty in responding because the required book was well known in Portugal and served as
Majorcan Jews, and in documents mentioning information was recorded in a variety of books. an instruction manual for pilots. In a passage at
the fifteenth-century Aragonese court, there is We can still speak of a "school of navigation" the end of Chapter I the cosmographer gives
reference to an Arte de Navegar (Art of Navi- metaphorically, because it was the navigators instructions on how to measure the distance
gation), a text which unfortunately has since who departed from the Algarve who contrib- encompassed by one meridian degree of the
been lost. uted their experience to resolving the difficulties earth by measuring the distance separating two
in an unprecedented way, thereby bringing points along a single meridian, and more pre-
* * * * * * * about the developments in technique. In this cisely by observing the altitude of the polestar
The growing nautical traffic in the Atlantic school, so to speak, each pilot was both appren- at points one degree apart from each other. In
in the course of the fifteenth century did not tice and master. As Luciano Pereira da Silva the context of Da Esfera this information was
completely change the methods of navigation wrote: "the school of Sagres was the planks of merely theoretical, because it required measur-
described above. Since Prince Henry encour- the caravels"—the practice of navigation rather ing the distance between the two points without
aged navigation beyond Cape Bojador, his ships than theory dictated the nautical solutions the the observer's leaving the meridian where he
having reached Sierra Leone at the time of his pilots developed. happened to be, which made the technique
death, it is often stated that he surrounded Let us look at the essential points of this new impracticable.
himself with scholars of different origins, who method of navigation. Sailors returning to the The instrument used in these observations
came together at some kind of academy at Algarve and later to Lisbon from their voyages, was the quadrant, and we know from a remark
Sagres at the southwestern tip of Portugal, which reached increasingly farther south along made by Diego Gomes that it was customary to
where he set up some sort of meteorological the African coast, met with serious difficulties write the name of the place where the star was

EUROPE AND THE MEDITERRANEAN WORLD 37