of a jelly-like consistency. He
does not profess to have visited Thule, and his account probably
refers to the existence of drift ice near the Shetlands.

All this new information was gathered together, and made accessible
to the Greek reading world, by ERATOSTHENES, librarian of Alexandria
(240-196 B.C.), who was practically the founder of scientific geography.
He was the first to attempt any accurate measurement of the size of
the earth, and of its inhabited portion. By his time the scientific
men of Greece had become quite aware of the fact that the earth
was a globe, though they considered that it was fixed in space
at the centre of the universe. Guesses had even been made at the
size of this globe, Aristotle fixing its circumference at 400,000
stadia (or 40,000 miles), but Eratosthenes attempted a more accurate
measurement. He compared the length of the shadow thrown by the sun
at Alexandria and at Syene, near the first cataract of the Nile,
which he assumed to be on the same meridian of longitude, and to be
at about 5000 stadia (500 miles) distance. From the difference in
the length of the shadows he deduced that this distance represented
one-fiftieth of the circumference of the earth, which would accordingly
be about 250,000 stadia, or 25,000 geographical miles. As the actual
circumference is 24,899 English miles, this was a very near
approximation, considering the rough means Eratosthenes had at his
disposal.

Having thus estimated the size of the earth, Eratosthenes then
went on to determine the size of that portion which the ancients
considered to be habitable. North and south of the lands known to
him, Eratosthenes and all the ancients considered to be either
too cold or too hot to be habitable; this portion he reckoned to
extend to 38,000 stadia, or 3800 miles. In reckoning the extent
of the habitable portion from east to west, Eratosthenes came to
the conclusion that from the Straits of Gibraltar to the east of
India was about 80,000 stadia, or, roughly speaking, one-third of
the earth's surface. The remaining two-thirds were supposed to be
covered by the ocean, and Eratosthenes prophetically remarked that
"if it were not that the vast extent of the Atlantic Sea rendered it
impossible, one might almost sail from the coast of Spain to that
of India along the same parallel." Sixteen hundred years later, as
we shall see, Columbus tried to carry out this idea. Eratosthenes
based his calculations on two funda