He Divided The Terms Latitude
And Longitude, Which, As We Have Already Stated, Were Introduced By
Artemidorus (A.C. 104)
Into degrees, and these degrees into their parts,
though this improvement was not reduced generally to practice before
Ptolemy, for
We are informed by him, that Marinus had the latitude of some
places and the longitude of others, but scarcely one position where he
could ascertain both.
With regard to the extent of Marinus' geographical knowledge, or the
accuracy of his details, we cannot form a fair judgment from the fragments
of his works which remain. According to Ptolemy, he had examined the
history of preceding ages, and all the information that had been collected
in his own time, comparing and rectifying them as he proceeded in his own
account.
It will be recollected that the Periplus of the Erythrean Sea did not trace
the African coast lower down than Rhapta; but Marinus mentions Prasum,
which, according to that hypothesis, which fixes it in the lowest southern
latitude, must have been seven degrees to the south of Rhapta. So far,
therefore, the knowlege of the ancients, in the time of Marinus, respecting
the east coast of Africa extended; but, as neither he nor Ptolemy mentions
a single place between Rhapta and Prasum, it is probable that the latter
was not frequently or regularly visited for the purposes of trade, but that
commercial voyages were still confined to the limit of Rhapta. We have just
stated that Prasum, according to the most moderate hypothesis, must be
fixed seven degrees to the south of Rhapta. Marinus, however, fixes it
either in thirty-five degrees south, or under the tropic of Capricorn. He
was led into this and similar errors by assigning too great a number of
stadia to the degree. Ptolemy endeavours to correct him, and places Prasum
in latitude 15, 30 south; it is remarkable that the Prasum of Ptolemy is
precisely at Mosambique, the last of the Arabian settlements in the
following ages, and the Prasum of Marinus, if under the tropic of
Capricorn, is the limit of the knowledge of the Arabians on this coast of
Africa.
Marinus, as quoted by Ptolemy, affirms that he was in possession of the
journals of two expeditions under the command of Septimus Flaccus and
Julius Maternus: the former of these officers set off from Cyrene, and the
latter from Leptis; and, according to Marinus, they penetrated through the
interior of Africa to the southward of the Equator, as far as a nation they
styled Agesymba. The error of Marinus with respect to the valuation of the
stadium, has led him to fix this nation in twenty-four degrees south
latitude; if allowance, however, be made for his error, the Agesymba will
still be placed under the Equator, - a great distance for a land expedition
to have readied in the interior of Africa. Flaccus reported that the
Ethiopians of Agesymba, were three months journeying to the south of the
Garamantes, and the latter were 5400 of the stadia of Marinus, distant from
Cyrene. According to the journal of Maternus, when the king of the
Garamantes set off to attack the people of Agesymba, he marched four months
to the south.
There are also some notices in Marinus of voyages performed along the coast
of Africa, between India and Africa, and along part of the coast of India;
he particularly mentions one Theophilus who frequented the coast of Azania,
and who was carried by a south-west wind from Rhapta to Aromata in twenty
days; and Diogenes, one of the traders to India, who on his return after he
had come in sight of Aromata, was caught by the north-east monsoon, and
carried down the coast during twenty-five days, till he reached the lakes
from which the Nile issues. Marinus also mentions a Diogenes Samius, who
describes the course held by vessels from the Indus to the coast of Cambay,
and from Arabia to the coast of Africa. According to him, in the former
voyage they sailed with the Bull in the middle of the heavens, and the
Pleiades in the middle of the main yard; in the latter voyage, they sailed
to the south, and by the star Canobus.
We now arrive at the name of Ptolemy, certainly the most celebrated
geographer of antiquity. He was a native of Alexandria, and flourished in
the reign of the emperor Marcus Antoninus. In the application of astronomy
to geography, he followed Hipparchus principally, and he seems from his
residence at Alexandria to have derived much information through the
merchants and navigators of that city, as well as from its magnificent and
valuable library. His great work, as it has reached us, consists almost
entirely of an elementary picture of the earth, (if it may be so called,)
in which its figure and size, and the position of places are determined.
There is only a short notice of the division of countries, and it is very
seldom that any historical notice is added. To this outline, it is supposed
that Ptolemy had added a detailed account of the countries then known,
which is lost.
His geography, such as we have described it, consists of eight books, and
is certainly much more scientific than any which had been previously
written on this science. In it there appears, for the first time, an
application of geometrical principles to the construction of maps: the
different projections of the sphere, and a distribution of the several
places on the earth, according to their latitude and longitude. Geography
was thus established on its proper principles, and intimately connected
with astronomical observations and mathematical science. The utility and
merit of Ptolemy's work seems to have been understood and acknowledged soon
after it appeared. Agathemidorus, who lived not long after him, praises him
for having reduced geography to a regular system; and adds, that he treats
of every thing relating to it, not carelessly, or merely according to the
ideas of his own, but to what had been delivered by more ancient authors,
adopting from them whatever he found consonant to truth.
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