ge of western Asia. In this way
the standard of value for every citizen of a country is as clearly defined
as the standard of weight, and every transaction in trade, with every
account of such transaction, involves that unit.

_United States coinage._--A brief statement of the system of coinage now
established in the United States may illustrate the definiteness of the
standards of value. The United States mint at Philadelphia and its
branches at New Orleans, Denver, San Francisco and Carson have the sole
authority for making coins. Any effort at coinage by outside parties is
criminal. The mint receives the gold and silver by weight and assay of
purity, melts and refines and mixes with alloy, to bring the mass to
required fineness, nine-tenths pure, and casts the metal into bars called
bullion. These bars are then most carefully assayed, and, if found of
exact standard purity, are rolled and drawn into plates the thickness of
the coins desired. From these plates disks are punched by machinery, each
disk being weighed, and if found too light thrown aside, if too heavy
reduced by filing, until every disk represents exactly the required weight
of the coin desired. The disks then pass through a milling machine which
raises the edges, and when cleaned by dilute acid and carefully dried, are
stamped by a steel die with some device covering both surfaces completely.
This effectually gives the seal of the nation to the purity and weight of
the coin, and, since it covers the whole surface, prevents the possibility
of reducing that weight without marring the coin.

_United States standards._--The system of coinage in the United States
since 1873 embraces standard coins of gold, silver, nickel and copper, but
gold alone actually furnishes the standards of value, all other coins
being at present subsidiary. Gold is coined for individuals free; that is,
a certain weight of metal presented at the mint is assayed, to determine
the exact weight of pure gold, and an equal weight of pure gold is
returned to the owner in coin. Sometimes a slight charge for the expense
of coinage is made and called seigniorage. At present no such charge is
made, for the reason that when a nation bears the cost of coinage, foreign
coins are kept from circulation, and its own coins are current everywhere.

The standard unit of value for the United States is 25.8 grains of gold
nine-tenths fine, and this is called a dollar, although no coin of this
weight is