MONEY AND THE MECHANISM OF EXCHANGE 163

high degree. Embodying high value in small bulk, the
cost of transport is reduced to a very small amount, while
their small liability to chemical change makes gold and
silver preferable to iron or copper, with their tendency to
rust or become covered with verdigris, involving the effective
loss of part of their substance. As to some other of the
commodities named above, wheat needs care and labour to
keep it from deteriorating if stored for a long time, cattle
lose condition if not fed. The latter point shows that,
however well fitted for use by pastoral peoples, cattle are
ansuited as a means of exchange for trading and manufacturing
 communities.
Ready divisibility without loss of value makes the medium
of exchange more convenient. Precious stones possess large
value in small bulk and lose nothing in storage, but their
division involves loss of value. The metals can be divided
and reunited if desired, without further expense than that
of the labour involved, and no loss of value. Ready division,
too, enables values of all magnitudes to be represented conveniently,
 Where gold represents moderate values, small
values would be represented by pieces of metal too small
to be convenient, and the device of using silver, and, for yet
smaller values, copper or bronze or nickel, enables the use
of pieces of convenient bulk for small as well as for large
transactions.
The precise equivalence of all units of the exchange
medium is also of great importance, and the ready recognition
of that equivalence, as also of the genuineness of what
professes to be the general medium of exchange. Only
members of a pastoral community could readily use cattle as
a medium of exchange, since discernment of fine beasts from
poor ones would be required. The metals, being homogeneous
 in nature, represent equivalent values in equal weights,
or equal bulk, if the purity is the same. The acceptance of
metal in payment by weight was long practised, but, for
‘etail transactions at any rate, is inconvenient. The device
of coinage, the cutting of the metal into pieces of fixed sizes
Or weights, bearing marks enabling them to be recognised,
orovides a means of making payments by tale, z.e. bv number