Agathodaemon, An
Artist Of Alexandria, Observing The Request In Which His Work Was Held,
Prepared A Set Of Maps To
Illustrate it, in which all the places mentioned
in it were laid down, with the latitudes and longitudes he assigned
Them.
The reputation of his geography remained unshaken and undiminished during
the middle ages, both in Arabia and Europe; and even now, the scientific
language which he first employed, is constantly used, and the position of
places ascertained by specifying their latitude and longitude.
It was not to be expected, however, that Ptolemy could accurately fix the
longitude and latitude of places in the remoter parts of the then known
world; his latitudes and longitudes are accordingly frequently erroneous,
but especially the latter. This arose partly from his taking five hundred
stadia for a degree of a great circle, and partly from the vague method of
calculating distances, by the estimate of travellers and merchants, and the
number of days employed in their journies by land, and voyages by sea. As
he took seven hundred stadia for a degree of latitude, his errors in
latitude are not so important; and though the latitude he assigns to
particular places is incorrect, yet the length of the globe, according to
him, or the distance from the extreme points north and south, then known,
is not far from the truth. Thus the latitude of Thule, according to
Ptolemy, is 64 degrees north, and the parallel through the cinnamon country
16 deg. 24' south, that is, 80 deg. 24' on the whole, a difference from the truth
of not more than six or seven degrees. It is remarked by D'Anville, and Dr.
Vincent coincides in the justice of the remark, that the grandest mistake
in the geography of Ptolemy has led to the greatest discovery of modern
times. Strabo had affirmed, that nothing obstructed the passage from Spain
to India by a westerly course, but the immensity of the Atlantic ocean;
but, according to Ptolemy's errors in longitude, this ocean was lessened by
sixty degrees; and as all the Portuguese navigators were acquainted with
his work, as soon as it was resolved to attempt a passage to India, the
difficulty was, in their idea, lessened by sixty degrees; and when Columbus
sailed from Spain, he calculated on sixty degrees less than the real
distance from that country to India. Thus, to repeat the observation of
D'Anville, the greatest of his errors proved eventually the efficient cause
of the greatest discovery of the moderns.
Beside the peculiar merit of Ptolemy, which was perceived and acknowledged
as soon as his work appeared, he possesses another excellence, which, as
far as we know, was first pointed out and dwelt upon by Dr. Vincent.
According to him, Ptolemy, in his description of India, serves as the point
of connection between the Macedonian orthography and the Sanscrit,
dispersing light on both sides, and showing himself like a luminary in the
centre. He seems indeed to have obtained the native appellations of the
places in India, in a wonderful manner; and thus, by recording names which
cannot be mistaken, he affords the means of ascertaining the country, even
though he gives no particulars regarding it. We have applied this remark to
India exclusively, but it might be extended to almost all the names of
places that occur in Ptolemy, though, as respects India, his obtaining the
native appellations is more striking and useful.
Having offered these general remarks on the excellencies and errors of
Ptolemy, we shall next proceed to give a short and rapid sketch of his
geographical knowledge respecting Europe, Asia, and Africa. On the
north-east of Europe he gives an accurate description of the course of the
Wolga; and further to the south, he lays down the course of the Tanais,
much nearer what it really is than the course assigned it by Strabo. He
seems to have been acquainted with the southern shores of the Baltic from
the western Dwina, or the Vistula, to the Cimbric Chersonesus: he also
describes part of the present Livonia. The Chersonesus, however, he
stretches two degrees too far to the north, and also gives it too great a
bend to the east. He applies the name of Thule to a country situated to the
north-east of Britain; if his usual error in longitude is rectified, the
position he assigns Thule would correspond with that of Norway. Such seem
to have been the limits of his Europe, unless, perhaps, he had some vague
idea of the south of Sweden.
He begins his geographical tables with the British isles; and here is one
of his greatest errors. According to him, the north part of Britain
stretches to the east, instead of to the north: the Mull of Galloway is the
most northern promontory, and the land from it bends due east. The Western
Islands run east and west, along the north shore of Ireland, the west being
the true north point in them. He is, however, on the whole, pretty accurate
in his location of the tribes which at that period inhabited Scotland.
Strabo had placed Ireland to the north of Britain, but in its true
latitude. Ptolemy's map, which is the first geographical document of that
island, represents it to the west of Britain, but five degrees further to
the north than it actually is. He delineates its general shape, rivers, and
promontories with tolerable accuracy, and some of his towns may be traced
in their present appellations, as Dublin in Eblana. It has already been
noticed that he was probably acquainted with the south of Sweden, and his
four Scandinavian islands are evidently Zealand, Funen, Laland, and
Falster. It is remarkable that his geography is more accurate almost in
proportion as it recedes from the Mediterranean. The form which he assigns
to Italy is much farther removed from the truth than the form of most of
the other European countries which he describes. His fundamental error in
longitude led him to give to the Mediterranean Sea a much greater extent
than it actually possesses.
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