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.
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