1902 Encyclopedia > Geography > Ptolemy. Strabo. Pliny. Cosmas.

(Part 6)

Ptolemy. Strabo. Pliny. Cosmas.

The most ancient maps that have reaches modern times are those which illustrate Ptolemny’s geography, but an earlier map made for Aristagoras, king of Miletus (500 B.C.), is minutely described by Herodotus. Ptolemy composed his system of geography in the reign of Antoninus Pius, about 150 A.D. His material consisted of all itineraries prepared by the Romans, proportions of the height of the gnomon and its shadow at the time of the equinoxes and solstices taken by different astronomers, calculations founded on the length of the longest days, and various reports of travelers and navigators. Ptolemy undertook the task of comparing and reducing this mass of crude material into one system, following the principles laid down by Hipparchus, but which had been neglected during the two centuries and a half since his time, even by such men as Strabo and Pliny. In Ptolemy’s work we find for the first time the mathematical principle of the construction of maps, as well as of several projections of the sphere.

The errors of Ptolemy arose from defective information, and the want in many instances, and especially as regards the remote parts of the then known world, of astronomical observations. He adopted the measure of a degree at 500 stadia; and the latitudes from the chief meridian of Rhodes, as first laid down by Eratosthenes, are tolerably correct. But the elements for determining the longitudes were still derived from itineraries, and error in latitude accumulated to the north and south of the central parallel.

Although Ptolemy was the first scientific geographer whose work has come down to us in a complete form, the earlier labours of Strabo, who lived in the reigns of Augustus and Tiberius, are of equal value, and we fortunately possess the whole of his 167 books. Pliny also devoted two books of his extensive work to geography; and the scattered geographical notices of other ancient writers were collected into one work of four volumes by Hudson, and published between 1698 and 1712, with notes by Dodwell. From the days of Ptolemy to the revival of letters in Europe, little was done towards the scientific improvement of geographical science, though military and commercial enterprise led to a great extension of knowledge of the earth’s surface.

After the dissolution of the Roman empire, Constantinople became the last refuge of arts, taste, and elegance; while Alexandria continued to be the emporium whence were imported the commodities of the East. The emperor Justinian sent two Nestorian monks to China, who returned with eggs of the silkworm concealed in a hollow cane, and thus silk manufactures were established in the Peloponnesus and the Greek Islands. It was also in the reign of Justinian that Cosmos Indicopleustes, and Egyptian merchant, made several voyages, and afterwards composed his Topographia Christiana, containing a particular description of India. The great outburst of Mahometan conquest was followed by an Arabian civilization, having its centres at Cordova and Baghdad, in connexion with which geography again received a share of attention.

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