164 . ECONOMIC PRINCIPLES

of coins, instead of by weighing the metal. The perfecting
of coinage secures some protection against fraud in this mode
of payment. The stamp of the mint is the guarantee of a
trusted agency as to the weight and purity of the metal in
the coin bearing the stamp, and the process serves also to
shape the metal into pieces of convenient shape and convenient
 proportions of value, of a hardness calculated to
endure wear and tear with but little loss, and of a design
such as to afford protection against fraudulent imitation or
the abstraction of part of the substance of the coin. The
hardness is partly secured by the proportion of alloy, partly
by the force with which the stamp strikes the coins. Usually
the standard metal for coinage contains 10 per cent. of alloy,
as gold and silver are too soft for use in a pure state.
English gold coins, however, contain one-twelfth part of alloy,
in this differing from those of all the rest of the world,
except Portugal; and English silver coins contain threefortieths
 of their weight of alloy, this being the traditional
fineness of English silver from the time when a moneyer’s
pound weight of silver represented the pound of value.
It was pointed out above that the facilitating of exchange
operations depended largely on the expression of the values,
of goods entering into exchanges, in terms of a general unit
of value. When a general medium of exchange is established
in use, values will naturally be expressed in terms of it.
But exchanges may be vastly facilitated, by such a common
mode of expressing values, even if the actual exchange be
not effected by the use of the thing in terms of which the
values entering into the exchange are stated. Such a condition
 occurs both in primitive and in advanced communities.
Thus the beaver-skin continues to serve as the unit of
measurement of values in some remote parts of Canada,
though the actual beaver-skin does not represent the unit of
value thus expressed. Actual skins, whether of beavers or
other animals, are valued at various rates in terms of the
beaver-skin, which is the traditional value unit. The goods
which are purchased, with the credit which the sale of the
produce of the chase provides, are also priced in beaver-skins.
In India, the Company’s rupee at one time served as a standard