of the Bisaltian silver mines that in the time preceding and immediately posterior to the Persian invasion silver was exceedingly abundant in all that region. It is then by no means unlikely that it required ten silver pieces of 220 grs. each to make the equivalent of one gold unit of 130 grs. With the exhaustion of the silver mines, and perhaps a greater output of gold, silver became dearer, and consequently 10 silver pieces of 170 grs. each were now equal to a gold stater. Abdera on the coast would come perfectly within the sphere of such changed conditions, and her standard would consequently likewise undergo modification. With Philip’s accession, fresh conquests and a general development of resources may have temporarily thrown more silver on the market, thus inducing him to revert to the 220 grs. standard, but the exploiting of the famous mines of Crenides increased the supply of gold to such an extent that by the time Alexander mounted his fathers throne gold stood to silver in the relation of 10:1, and it was found extremely convenient to coin this on the same footing as gold, 10 silver pieces of 135 grs. being exactly equal to the gold stater of like weight. A like explanation applies to the coinage of Thrace. Amongst the Thracian tribes who dwelt near Mount Pangaeum and worked the gold and silver mines of that region the art of coining had been known from the 6th century B.C. and they issued silver coins of about 160 grs. This is regarded by some as debased Babylonian or Persic standard. But it is far more rational to suppose that in that region gold was more plentiful in proportion to silver than it was at that time further west in Macedonia, and accordingly a certain number of silver didrachms of 160 grs. were found to represent the gold stater or ox-unit. It seems most unlikely that a people long acquainted with both gold and silver could not devise for themselves a simple method of making some convenient number of silver pieces be equivalent to one gold, and that, on the contrary, having once obtained a certain standard fixed for silver in Asia Minor, at a time when gold was to silver as 13:1, they would blindly cleave to this standard, no matter how great a change took place in the relation of the metals. In face of the statements of Xenophon and Polybius already quoted and the fact that Solon deliberately constructed a new silver standard, it is simply impossible to believe such a doctrine.