The conquests of the Arabs affected the knowledge of geography
in a twofold way: by bringing about the Crusades, and by renewing
the acquaintance of the west with the east of Asia. The Arabs were
acquainted with South-Eastern Africa as far south as Zanzibar and
Sofala, though, following the views of Ptolemy as to the Great
Unknown South Land, they imagined that these spread out into the
Indian Ocean towards India. They seem even to have had some vague
knowledge of the sources of the Nile. They were also acquainted
with Ceylon, Java, and Sumatra, and they were the first people to
learn the various uses to which the cocoa-nut can be put. Their
merchants, too, visited China as early as the ninth century, and we
have from their accounts some of the earliest descriptions of the
Chinese, who were described by them as a handsome people, superior
in beauty to the Indians, with fine dark hair, regular features,
and very like the Arabs. We shall see later on how comparatively
easy it was for a Mohammedan to travel from one end of the known
world to the other, owing to the community of religion throughout
such a vast area.

Some words should perhaps be said on the geographical works of the
Arabs. One of the most important of these, by Yacut, is in the form
of a huge Gazetteer, arranged in alphabetical order; but the greatest
geographical work of the Arabs is by EDRISI, geographer to King Roger
of Sicily, 1154, who describes the world somewhat after the manner
of Ptolemy, but with modifications of some interest. He divides the
world into seven horizontal strips, known as "climates," and ranging
from the equator to the British Isles. These strips are subdivided
into eleven sections, so that the world, in Edrisi's conception,
is like a chess-board, divided into seventy-seven squares, and his
work consists of an elaborate description of each of these squares