N.B.  The modern Names are given in Italics. 
  By
  Sir J. Emerson Tennent.]

The extent and accuracy of Ptolemy’s information is so surprising, that it has given rise to surmises as to the sources whence it could possibly have been derived.[1] But the conjecture that he was indebted to ancient Phoenician or Tyrian authorities whom he has failed to acknowledge, is sufficiently met by the consideration that these were equally accessible to his predecessors.  The abundance of his materials, especially those relating to the sea-borde of India and Ceylon, is sufficient to show that he was mainly indebted for his facts to the adventurous merchants of Egypt and Arabia, and to works which, like the Periplus of the Erythroean Sea (erroneously ascribed to ARRIAN the historian, but written by a merchant probably of the same name), were drawn up by practical navigators to serve as sailing directions for seamen resorting to the Indian Ocean.[2]

[Footnote 1:  HEEREN, Hist.  Researches, vol. ii.  Appendix xii.]

[Footnote 2:  LASSEN, De Taprob.  Ins. p. 4.  From the error of Ptolemy in making the coast of Malabar extend from west to east, whilst its true position is laid down in the Periplus, VINCENT concludes that he was not acquainted with the Periplus, as, anterior to the invention of printing, cotemporaries might readily be ignorant of the productions of each other (VINCENT, vol. ii. p. 55).  Vincent assigns the composition of the Periplus to the reign of Claudius or Nero, and Dodwell to that of M. Aurelius, but Letronne more judiciously ascribes it to the period of Severus and Caracalla, A.D. 198,210, fifty years later than Ptolemy.  The author, a Greek of Alexandria and a merchant, never visited Ceylon, though he had been as far south as Nelkynda (the modern Neliseram), and the account which he gives from report of the island is meagre, and in some respects erroneous.  ARRIANI Periplus Maris Eryth.; HUDSON, vol. i. p. 35; VINCENT, vol. ii. p. 493.]

So ample was the description of Ceylon afforded by Ptolemy, that for a very long period his successors, AGATHEMERUS, MARCIANUS of Heraclea, and other geographers, were severally contented to use the facts originally collected by him.[1] And it was not till the reign of Justinian, in the sixth century, that COSMAS INDICO-PLEUSTES, by publishing the narrative of Sopater, added very considerably to the previous knowledge of the island.

[Footnote 1:  AGATHEMERUS, Hudson Geog., l. ii. c. 7,8.; MARCIANUS HERACLEOTA, Periplus, Hudson, p. 26.  STEPHANUS BYZANTINUS, in verbo “Taprobane.”  Instead of the expression of PTOLEMY that Taprobane [Greek:  ekaleito palai Simoundon], which MARCIANUS had rendered [Greek:  Palaisimioundou], STEPHANUS transposes the words as if to guard against error, [Greek:  palai men ekaleito Simoundou], &c.  The prior authority of PTOLEMY, however, serves to prolong the mystery, as he calls the capital Palaesimundum.]