y would mean permanent profits
for the _entrepreneur_; and it can be asserted without hesitation that
it would not do so if the final productivity theory of interest is
sound, that is, if capital commands in the market a rate of interest
which corresponds to the amount that the marginal increment of it will
actually produce.

_The Rate of Expansion of Currency distinguished from the Absolute
Amount of Increase._--The extent to which any currency is capable of
raising prices by a continued expansion depends, not on the absolute
amount of that expansion, but on the percentage of enlargement that
takes place within a given time. Moreover, a given percentage of
increase _per annum_ may be maintained as well by one metal as by two.
If the gold and the silver money of the world were each increased by
one per cent a year, prices would have the same trend under a currency
made of one metal as under a currency made of both. If, on the other
hand, all the currencies were based on gold only, a change to a
bimetallic system would at once make a single great enlargement of the
volume of money; but after this the rate of enlargement would be no
greater than it was under the single standard. _In the transition_
from a gold to a bimetallic currency, we should get rapidly rising
prices; after the change had been completed, we should have a currency
expanding as before at the one per cent rate. If the volume of
business were to increase at the rate of two per cent a year, while
other influences affecting prices were to remain unchanged, the
currency would not expand as rapidly as the demand for it, and prices
would not only fall, but would fall at the same rate as if only one
metal had been used. Use ten metals instead of two,--make coins of
tin, platinum, copper, nickel, etc.,--and if the grand composite still
insures the one per cent rate of general increase of metallic money,
prices will vary as they would have varied with a currency of gold
alone. Wholly transitional, under such circumstances, is the rise in
prices secured by the adoption of bimetallism. It is gained by adding
to the stock of gold now used for ultimate payments an existing stock
of silver.

_Why Metallic Currency of Any Kind gains, in the Long Run, in
Purchasing Power._--In the long run, almost any metallic coin of a
fixed weight will gain in its purchasing power. Silver would do this
as well as gold; and so would a composite coinage made of ten metals.
The law of