AL IDRISI MAP

Al-Idrisi's Rome had an oriental magnificence; ships with their freight sailed up the Tiber to be "drawn thus loaded right up to the very shops of the merchants." There were 1,200 churches; the streets were paved with blue and white marble; in a magnificent church encrusted with emeralds stood an altar supported by 12 statues of pure gold, with ruby eyes. And the city's "prince," he wrote, "is called the Pope."

Al-Idrisi presented the planisphere, a silver celestial sphere and the book to his patron in 1154, just a few weeks before Roger died at 58, probably of a heart attack; he went on to compose another geographical work for William I, Roger's successor. This work is said to have been even more extensive than his earlier one, but only a few extracts have survived.

In 1160, however, Sicilian barons rose in rebellion against William and during the disorders looted the palace; in a great fire in the courtyard, they burned government records, books and documents—including a new Latin edition of Roger's book which al-Idrisi had presented to William. At the same time, the silver planisphere and celestial sphere disappeared, apparently cut up and melted down.

Since the barons had attacked the Muslims of Sicily with particular ferocity—killing, among many others, a famous poet named Yahya ibn al-Tifashi—al-Idrisi fled to North Africa where, six years later, he died.

As he had brought the Arabic text with him, however, his great work lived on, winning widespread fame, serving as a model for Muslim geographers and historians for centuries and providing the great Muslim historian, Ibn Khaldun, with practically all his geographical knowledge.

It was not, however, available in Europe. Although the Arabic text of Roger's Book was published in Rome by the Medici press in 1592, it was not again available to Europeans in Latin until the 17th century. In the 1400's, therefore, Christopher Columbus had to rely on other sources of information. Using a globe prepared by a German cartographer named Martin Behaim—based on Ptolemy's miscalculations—Columbus also added in Marco Polo's equally misleading estimates of distances and concluded, incorrectly, that by sailing west from Spain he could reach Japan or India after no more than a 4,000-mile voyage.

It is a curious thought that had Columbus been aware of the true distance—from al-Idrisi's estimates—he might have hesitated to undertake his epoch-making voyage and might never have discovered that new world which came to light one morning on the far side of the "Sea of Darkness."

Frances Gies has collaborated with her husband on five books, four of them about the Middle Ages. A book on medieval women is next.

This article appeared on pages 14-19 of the July/August 1977 print edition of Saudi Aramco World.