All this new knowledge of East and West was soon gathered
together by Eratosthenes, the learned librarian of Alexandria. He was the
founder of scientific geography. Before his time some students had already
concluded that the earth is spherical and not flat, as had been taught in the
Homeric poems. Guesses had even been made of the size of the earth.
Eratosthenes by careful measurements came within a few thousand miles of its
actual circumference. Having estimated the size of the earth, Eratosthenes went
on to determine how large was its habitable area. He reached the conclusion that
the distance from the strait of Gibraltar to the east of India was about
one-third of the earth's circumference. The remaining two-thirds, he thought,
was covered by the sea. And with what seems a prophecy he remarked that, if it
was not for the vast extent of the Atlantic Ocean, one might almost sail from
Spain to India along the same parallel of latitude.
The next two centuries after Eratosthenes saw the spread
of Roman rule over Greeks and Carthaginians in the Mediterranean and over the
barbarous inhabitants of Gaul, Britain, and Germany. The new knowledge thus
gained was summed up in the Greek Geography by Ptolemy  of
Alexandria. His famous map shows how near he came to the real outlines both of
Europe and Asia.
THE PTOLEMAIC SYSTEM
Ptolemy was likewise an eminent astronomer. He believed
that the earth was the center of the universe and that the sun, planets, and
fixed stars all revolved around it. This Ptolemaic system was not overthrown
until the grand discovery of Copernicus in the sixteenth century of our era.