in the incuse exactly the same form as that in relief on the obverse.
At first sight the result of this great variety of local units apparently places impassable barriers to trade, but a knowledge of the actual facts of barbarous communities and their monetary systems as they exist in our time easily dispels this impression. I quoted above (p. 46) the words of Mohammed Ibn-Omar, wherein he points out that every separate district in the Soudan has its own lower unit or units, whilst everywhere alike the ox and the slave are the higher units; these local units are equated one to the other, so that there is no difficulty in trading. The same holds true of ancient Greece; the tortoise-shell of Aegina may have been reckoned equal to a certain amount of Attic olive oil or to a jar of wine of certain size, which formed the unit of commerce at Thasos and Chios, whilst in its turn a jar of wine was reckoned as equivalent to a package of silphion from Cyrene, a kettle from Crete, or an axe, or certain number of axes, or half-axes from Tenedos, or an ox-hide shield from Boeotia. All were sub-multiples of the ox, and had a fixed value in gold, and later in silver, as weighed against grains of corn. This supposition is in complete accord with the system revealed to us in the Homeric Poems, and is confirmed by the evidence drawn from barbarous races in modern times. It is likewise to be borne in mind that the tendency to place religious and mythological types on Greek coins was one especially developed in the later but not in the earliest period of coinage. No doubt aesthetic considerations played a large part in the adoption of such types, which came especially into prominence when Greek art was at its height. On the early coins one simple type is the rule, whilst at a later stage, besides the old national type, many adjuncts and symbols are added. Contrast the early coins of Athens with the later. The archaic issues have an olive spray and an owl, the later have not merely the owl, but an amphora, and a symbol in the field alluding to the legend of Triptolemus. Again, at Argos the early coins have simply the wolf or half-wolf or wolf's head, with a large A on the reverse, but in the later times the A is accompanied by symbols, such as a crescent
