The Story of Geographical Discovery | Page 7

Alexander the Great (333 B.C.), and he is especially interesting to us as
having been the first civilised person who can be identified as having
visited Britain. He seems to have coasted along the Bay of Biscay, to
have spent some time in England,--which he reckoned as 40,000 stadia
(4000 miles) in circumference,--and he appears also to have coasted
along Belgium and Holland, as far as the mouth of the Elbe. Pytheas is,
however, chiefly known in the history of geography as having referred
to the island of Thule, which he described as the most northerly point
of the inhabited earth, beyond which the sea became thickened, and 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 fundamental lines, corresponding in a way to
our equator and meridian of Greenwich: the first stretched, according to

him, from Cape St. Vincent, through the Straits of Messina and the
island of Rhodes, to Issus (Gulf of Iskanderun); for his starting-line in
reckoning north and south he used a meridian passing through the First
Cataract, Alexandria, Rhodes, and Byzantium.
The next two hundred years after Eratosthenes' death was filled up by
the spread of the Roman Empire, by the taking over by the Romans of
the vast possessions previously held by Alexander and his successors
and by the Carthaginians, and by their spread into Gaul, Britain, and
Germany. Much of the increased knowledge thus obtained was
summed up in the geographical work of STRABO, who wrote in Greek
about 20 B.C. He introduced from the extra knowledge thus obtained
many modifications of the system of Eratosthenes, but, on the whole,
kept to his general conception of the world. He rejected, however, the
existence of Thule, and thus made the world narrower; while he
recognised the existence of Ierne, or Ireland; which he regarded as the
most northerly part of the habitable world, lying, as he thought, north
of Britain.
Between the time of Strabo and that of Ptolemy, who sums up all the
knowledge of the ancients about the habitable earth, there was only one
considerable addition to men's acquaintance with their neighbours,
contained in a seaman's manual for the navigation of the Indian Ocean,
known as the Periplus of the Erythræan Sea. This gave very full and
tolerably accurate accounts of the coasts from Aden to the mouth of the
Ganges, though it regarded Ceylon as much greater, and more