According To Him, It Occupies Nearly Sixty-Five
Degrees; And It Is A Singular Circumstance, As Well As A Decisive
Proof of
the influence of his authority, as well of the slow progress of accurate
and experimental geography, that his
Mensuration of this sea was reputed as
exact till the reign of Louis XIV., when it was curtailed of nearly
twenty-five degrees by observation.
The principal points in the geography of Asia, as given by Ptolemy, respect
the coasts of India, the route to the Seres, and the Caspian sea. His
delineation of India is equally erroneous with his delineation of the
British Isles: according to him, it stretches in a right line from west to
east, a little to the south of a line drawn between the Ganges and the
Indus. He possessed, however, information respecting places in the farther
peninsula of India, the locality of several of which, by comparing his
names with the Sanscrit, may be traced with considerable certainty. He
assigns to the island of Ceylon a very erroneous locality, arising from his
error respecting the form of India, and likewise an extent far exceeding
the truth. He is the first author, however, who mentions the seven mouths
of the Ganges. The route to the Seres, which he describes, has been already
noticed: it is remarkable that the latitude which he assigns to his Sera
metropolis, is within little more than a degree of the latitude of Pekin,
which, in the opinion of Dr. Vincent, is one of the most illustrious
approximations to truth that ancient geography affords. His description of
Arabia is, on the whole, accurate; he has, however, greatly diminished the
extent of the Arabian Gulf, and by at the same time increasing the size of
the Persian, he has necessarily given an erroneous form to this part of
Asia. The ancient opinion of Herodotus, that the Caspian was a sea by
itself, unconnected with any other, which was overlooked or disbelieved by
Strabo, Arrian, &c. was adopted by Ptolemy, but he erroneously describes it
as if its greatest length was from east to west. The peninsula to which he
gives the name of the Golden Chersonesus, and which is probably Malacca, he
describes as stretching from north to south: to the east of it he places a
great bay, and in the most distant part of it the station of Catigara.
Beyond this, he asserts that the earth is utterly unknown, and that the
land bends from this to the west, till it joins the promontory of Prasum in
Africa, at which place this quarter of the world terminated to the south.
Hence it appears that he did not admit a communication between the Indian
and Atlantic oceans, and that he believed the Erythrean sea to be a vast
basin, entirely enclosed by the land.
Strabo and Pliny believed that Africa terminated under the torrid zone, and
that the Atlantic and Indian oceans joined. Ptolemy, as we have just seen,
rejected this idea, and following the opinion of Hipparchus, that the earth
was not surrounded by the ocean, but that the ocean was divided into large
basins, separated from each other by intervening land, maintained, that
while the eastern coast of Africa at Cape Prasum united with the coast of
Asia at the bay of the Golden Chersonesus, the western coast of Africa,
after forming a great gulf, which he named Hespericus, extended between the
east and south till it joined India. The promontory of Prasum was
undoubtedly the limit of Ptolemy's knowledge of the east coast of Africa:
the limit of his knowledge of the west coast is not so easily fixed: some
suppose that it did not reach beyond the river Nun; while others, with more
reason, extend it to the Gulf of St. Cyprian, because the Fortunate
Islands, which he assumed as his first meridian, will carry his knowledge
beyond the Nun; and because, at the Gulf of St. Cyprian, the coast turns
suddenly and abruptly to the east, in such a manner as may be supposed to
have led Ptolemy to believe that it stretched towards and joined the coast
of India.
Of some of the interior parts of Africa Ptolemy possessed clear and
accurate information; regarding others, he presents us with a mass of
confused notions. He clearly points out the Niger, though he fixes its
source in a wrong latitude. In the cities of Tucabath and Tagana, which he
places on its banks, may perhaps be recognized Tombuctoo and Gana. The most
striking defect in his geography of the interior of Africa is, that he does
not allow sufficient extent to the great desert of Sahara, while the
southern parts are too much expanded. He places the sources of the Nile,
and the Mountains of the Moon in south latitude thirteen, instead of north
latitude six or seven; but the error of latitude is not so remarkable and
unaccountable as the very erroneous latitude which he assigns to Cape
Aromata, on a coast which was visited every year by merchants he must have
seen at Alexandria. The most difficult point to explain in Ptolemy's
central Africa is the river Gir, which he describes as equal in length to
the Niger, and running in the same direction, till it loses itself in the
same lake. What this river is, geographers have not agreed. It is mentioned
by Claudian, as resembling the Nile in the abundance of its waters.
Agethimedorus, a geographer of the third century, regards it and the Niger
as the same river.
What then was the amount of the knowledge of the ancients, as it existed
among the Romans, in the height of their power, respecting the form,
extent, and surface of the globe? If we view a map drawn up according to
their ideas, we are immediately struck with the form they assigned the
world, and perceive with what propriety they called the extent of the world
from east to west longitude or _length_, and the extent from north to
south latitude, or _breadth_. In some maps, especially that drawn up
from the celebrated Peutingerian Tables, which contain an itinerary of the
whole Roman empire, thirty-five degrees of longitude occupy twenty-eight
feet eight inches, whereas thirteen degrees of latitude are compressed
within the space of one foot.
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