Arim, "the World's Summit"; from Ptolemy the sacred number of 360
degrees of longitude was certainly derived, beautifully corresponding to
the days of the year, and neatly divided into 180 of land or habitable
earth and 180 of sea, or unharvested desert. With the seven climates
they made correspond the great Empires of the world--chief among which
they reckoned the Caliphate (or Bagdad), China, Rome, Turkestan, and
India.

[Footnote 10: In which the habitable quarter of the world, situated
mainly in the Northern Hemisphere, was just about twice as long as it
was broad.]

The sacred city of Odjein had been the centre of most of the earlier
Oriental systems; in the Arabic form of Arim ("The Cupola of the
Earth"), it became the fixed point round which circled mediæval theories
of the world's shape. "Somewhere in the Indian Ocean between Comorin and
Madagascar," became the compromise when the mountain could not be found
off any of the known coast-lines; it was mixed up with notions of the
Roc, and the Moon Mountains in Africa, of the Magnet Island and of the
Eastern Kingdom made out of one vast pearl; and even in Roger Bacon it
serves as an algebraic sign for a mathematical centre of the world.

The enlargement of knowledge, though forcing upon Arabic science a
conviction of Ptolemy's mistake in over-extending the limits of the
world known to him, only led to the invention of a scholastic
distinction between the real and the traditional East and West, while
the confusion was made perfect by the travestied history always so
popular among Orientals. The "Gades of Alexander and Hercules," the
farthest points east and west, were named after the mythical conquests
of the real Iskander and the mythical hero of Greeks and Phoenicians.