IN´DICUS OCEANUS(ὁ Ἰνδικὸς ὠκεανός, Agath. 2.14; τὸ Ἰνδικὸν πέλαγος, Ptol. 7.1.5). The Indian Ocean of the ancients may be considered generally as that great sea which washed the whole of the southern portion of India, extending from the parallel of longitude of the mouths of the Indus to the shores of the Chersonesus Aurea. It seems, in-deed, to have been held by them as part, however, of a yet greater extent of water, the limits of which were undefined, at least to the southwards, and to which they gave the generic name of the Southern Sea. Thus Herodotus speaks of ἡ νοτίη θάλασσαin this sense (4.37), as does also Strabo (2. p. 121); Diodorus calls it ἡ κατὰ μεσημβρίαν ὠκεανός (iii, 38), while the Erythraean sea, taken in its most extended meaning, doubtless conveyed the same sense. (Hdt. 2.102, 4.37; compared with Strab. 1. p. 33.) Ptolemy gives the distances across this sea as stated by seafaring men; at the same time he guards against their over-statements, by recording his opinion in favour of no more than one-third of their measurements: this space he calls 8670 stadia (1.13.7). The distance along its shores, following the indentations of the coast-line, he estimates, on the same authority, at 19,000 stadia. It is evident, however, that Ptolemy himself had no clear idea of the real form of the Indian Ocean, and that lie inclined to the opinion of Hipparchus, Polybius, and Marinus of Tyre, that it was a vast inland sea the southern portion of it being bounded by the shores of an unknown land which he supposed to connect Cattigara in the Chersonesus Aurea with the promontory of Prasum (now Cape Delgado) in Africa (comp. 4.9. § § 1, 3, 7.3. § § 1, 3, 6). The origin of this error it is not easy now to ascertain, but it seems to have been connected with one which is found in the historians of Alexander's expedition, according to which there was a connection between the Indus and the Nile, so that the sources of the Acesines ( Chenáb) were confounded with those of the Nile. (Arrian, 6.1.) Strabo, indeed, appears to have had some leaning to a similar view, in that he connected the Erythraean with the Atlantic sea (2. p. 130); which was also the opinion of Eratosthenes (Strab. 1. p. 64). The Indian Ocean contains at its eastern end three principal gulfs, which are noticed in ancient authors,—the SINUS PERIMULICITS(Ptol. 7.2.5), in the Chersonesus Aurea (probably now the Straits of Malacca); the SINUS SABARACUS(Ptol. 7.2.4), now the Gulf of Martaban;and the SINUS GANGETIOUS,or Bay of Bengal.
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