If we reflect on the rude and imperfect state of science at this period, the paucity and inadequacy of the instruments by means of which it might be improved, and the superstitions and prejudices which opposed the removal of error or the establishment of truth, we shall not be disposed to question the justice of the panegyric pronounced by Pliny on Eratosthenes.  This author, after detailing all that was then known on the subject of the circumference of the earth, and on the distances which had been ascertained by actual admeasurement, or approximated by analogy or probable conjecture, between the most remarkable places on its surface, adds, that Eratosthenes, whose acuteness and application had advanced him far in every branch of knowledge, but who had outstripped all his predecessors or contemporaries in that particular branch which was connected with the admeasurement of the earth, had fixed its circumference at 250,000 stadia; a bold and almost presumptuous enterprize, (improbum ausum,) but which had been conducted with so much judgment, and on such sound principles, that it commanded and deserved our credit.  Hipparchus, who was distinguished for his correctness and diligence in every part of geometrical and astronomical science, and who had specially exerted those qualities in his endeavours to correct the errors of Eratosthenes, had been able to add only the comparatively small extent of 25,000 stadia to the computation of Eratosthenes.—­Plin.  Nat.  Hist. lib. ii. c. 108.

Eratosthenes seems, from the nature of his studies, not to have availed himself so much as he might have done of the treasures contained in the Alexandrian library under his care, to correct or extend the geographical knowledge of his contemporaries.  The same observation will not apply to Agatharcides, who was president of the library after Eratosthenes.  The exact time at which he flourished is not known:  according to Blair, he was contemporary with Eratosthenes, though younger than him, and flourished 177 A.C., Eratosthenes having died at the age of eighty-one, in the year 194 A.C.  Dodwell, however, fixes him at a later period; viz. 104 A.C.; but this date must be erroneous, because Artemidorus of Ephesus, who evidently copies Agatharcides, undoubtedly lived 104 A.C.  Agatharcide’s was born at Cnidus in Caria:  no particulars are known respecting him, except that he was president of the Alexandrian library, in the reign of Ptolemy Philometor, if he flourished 177 A.C.; and in the reign of Ptolemy Lathyrus, if, according to Dodwell, he did not flourish till 104 A.C.

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