Our concern with Agatharcides relates only to the geographical knowledge which his writings display; and even of that we can only select such parts as are most important, and at the same time point out and prove the advances of geographical knowledge, and of commercial enterprize; before, however, we leave him, we may add one fact, not immediately relating to our peculiar subject, which he records:  after stating that the soil of Arabia was, as it were, impregnated with gold, and that lumps of pure gold were found there from the size of an olive to that of a nut, he adds, that iron was twice, and silver ten times, the value of gold.  If he is accurate in the proportionate values which he respectively assigns to these metals, it proves the very great abundance of gold; since, in most of the nations of antiquity, the values of gold and silver were the reverse of what they were in Arabia, gold being ten times the value of silver.  The comparative high value of iron to gold is still more extraordinary, and seems to indicate not only a great abundance of the latter metal, but also a great scarcity of the former, or a very great demand for it in consequence of the extended and improved state of those arts and manufactures in which iron is an essential requisite, and which indicate an advanced degree of knowledge and civilization.  We are not aware of a similar fact, with respect to the proportionate value of iron and silver, being recorded of any other nation of antiquity.  It is not to be supposed, however, that the cheapness of gold, measured by iron and silver, could long continue in Arabia, unless we believe that their intercourse with other nations was very limited; because a regular and extensive intercourse would soon assimilate, in a great degree at least, the value of gold measured by iron and silver, as it existed in Arabia, to its value, as measured by the same metals in those countries with which Arabia traded.

But to return from this slight digression;—­Artemidorus has been already mentioned as a geographer subsequent to Agatharcides, who copied Agatharcides, and from whom Diodorus Siculus and Strabo in their turns copied.  There were two ancient writers of this name born at Ephesus; the one to whom we have alluded, is supposed to have lived in the reign of Ptolemy Lathyrus, A.C. 169; by others he is brought down to A.C. 104.  Little is known respecting him; nor does he seem to have added much to geographical science or knowledge:  he is said by Pliny to have first applied the terms of length and breadth, or latitude and longitude.  By comparing those parts of Diodorus Siculus and Strabo, which they avowedly copy from him, with the track of Agatharcides:  in the Red Sea, we are enabled to discover only a few additions of importance to the geographical knowledge supplied by the former:  Agatharcides, it will be remembered, brings his account of the African side of the Red Sea no lower down than Ptolemais:  he does not even mention the expedition