The only work of his which is preserved, is a Treatise on the Erythraean Sea; and this we possess only in the Bibliotheca of Photius, and incorporated in the history of Diodorus Siculus. The authority of Agatharcides was very high among the ancients. Strabo, Pliny, and Diodorus, always mention him with the utmost respect, and place implicit confidence in his details. Diodorus expressly states that Agatharcides and Artemidorus (who, as we have already mentioned, was merely his copyist) are the only authors who have written truth concerning Egypt and Ethiopia; and Strabo follows him in all that relates to the latter country, the countries lying to the south of Egypt, and the western coast of Arabia. In fact, for nearly 200 years, the ancient historians and geographers drew all the information they possessed respecting the portions of the world embraced in the work of Agatharcides from that work. It has been well observed, "that when Pliny speaks of the discoveries on the coast of Malabar in his own age, and adds, that the names he mentions are new, and not to be found in previous writers, we ought to consider him as speaking of all those who had followed the authority of the Macedonians, or the school of Alexandria; of which, in this branch of science, Eratosthenes and Agatharcides were the leaders." From the circumstance that Strabo appeals very frequently to the authority of Eratosthenes, in conjunction with that of Agatharcides, it has been conjectured, that the work of the latter contains all that the former knew, with the addition of his own information; and this conjecture is highly probable, considering that Agatharcides had access to the sources whence Eratosthenes drew his information; to the works of Eratosthenes themselves, which of course would be deposited in the Alexandrian library; and to all the additional works which had enriched the library from the time of Eratosthenes, as well as the additional information which the extensive commerce of Alexandria would supply. The work of Agatharcides, therefore, having been in such estimation by the ancient historians and geographers, and the only source from which, during 200 years, they drew their information, and having been compiled by a person, who, it is probable, had better and fuller means of rendering it accurate and complete than any of his contemporaries enjoyed; it will be proper to give a pretty full abstract of the most interesting and important part of its contents.