science by conjecture, than in Ptolemy's scheme of the world (_c._ A.D.
130). His chief predecessors, Eratosthenes and Strabo, had left much
blank space in their charts, and had made many mistakes in detail, but
they had caught the main features of the Old World with fair accuracy.
Ptolemy, in trying to fill up what he did not know from his inner
consciousness, evolved a parody of those features. His map, from its
intricate falsehood, backed as it was by the greatest name in
geographical science, paralysed all real enlargement of knowledge till
men began to question, not only his facts, but his theories. And as
all modern science, in fact, followed the progress of world-knowledge,
or "geography," we may see how important it was for this revolution to
take place, for Ptolemy to be dethroned.

[Illustration: THE WORLD ACCORDING TO PTOLEMY. (SEE LIST OF MAPS)]

The Arabs, commanding most of the centres of ancient learning (Ptolemy's
own Alexandria above all), riveted the pseudo-science of their
predecessors on the learned world, along with the genuine knowledge
which they handed down from the Greeks. In many details they corrected
and amplified the Greek results. But most of their geographical theories
were mere reproductions of Ptolemy's, and to his mistakes they added
wilder though less important confusions or inventions of their own. The
result of all this, by the tenth century A.D., was a geography, based
not on knowledge, but on ideas of symmetry. It was a scheme fit for the
_Arabian Nights_.

And how did Ptolemy lend himself to this?

His chief mistakes were only two;--but they were mistakes from which at
any rate Strabo and most of the Greek geographers are free. He made the