n more famous measurement of
Eratosthenes, appears to have been practically the sole guide as to
the size of the earth throughout the later periods of antiquity, and,
indeed, until the later Middle Ages.

As becomes a writer who is primarily geographer and historian rather
than astronomer, Strabo shows a much keener interest in the habitable
portions of the globe than in the globe as a whole. He assures us that
this habitable portion of the earth is a great island, "since wherever
men have approached the termination of the land, the sea, which we
designate ocean, has been met with, and reason assures us of the
similarity of this place which our senses have not been tempted to
survey." He points out that whereas sailors have not circumnavigated the
globe, that they had not been prevented from doing so by any continent,
and it seems to him altogether unlikely that the Atlantic Ocean is
divided into two seas by narrow isthmuses so placed as to prevent
circumnavigation. "How much more probable that it is confluent and
uninterrupted. This theory," he adds, "goes better with the ebb and flow
of the ocean. Moreover (and here his reasoning becomes more fanciful),
the greater the amount of moisture surrounding the earth, the easier
would the heavenly bodies be supplied with vapor from thence." Yet he is
disposed to believe, following Plato, that the tradition "concerning
the island of Atlantos might be received as something more than idle
fiction, it having been related by Solon, on the authority of the
Egyptian priests, that this island, almost as large as a continent, was
formerly in existence although now it had disappeared."(2)

In a word, then, Strabo entertains no doubt whatever that it would
be possible to sail around the globe from Spain to India. Indeed, so
matter-of-fact an inference was this that the feat of Columbus would
have seemed less surprising in the first century of our era than it did
when actually performed in the fifteenth century. The terrors of the
great ocean held the mariner back, rather than any doubt as to where he
would arrive at the end of the voyage.

Coupled with the idea that the habitable portion of the earth is an
island, there was linked a tolerably definite notion as to the shape
of this island. This shape Strabo likens to a military cloak. The
comparison does not seem peculiarly apt when we are told presently that
the length of the habitable earth is more than twice its breadth. This
idea