166 ECONOMIC PRINCIPLES

the new crop is ready. But the dependence of the annual
consumption on the production of the year immediately
preceding is obvious, and changes in the yield from year to
year are fully reflected in the changes in supply available for
use, and hence in the value of the product. In the case of
gold, the supply available for current use is a large multiple
of the output of the mines for a year, still more so of the
Auctuations in that output from year to year. These fluctuations
 of output can, therefore, have comparatively little effect
on the value of gold, that is on the proportion in which gold
exchanges for other commodities. With an accumulated
supply of gold in monetary form, or held as bullion in bank
vaults, amounting to nearly £1,000,000,000in value, an output
of £60,000,000 or even £70,000,000 yearly cannot be a cause
of such changes in supply as to change the value of gold
with serious rapidity. This cause of relative stability, namely
comparative stability of supply, cannot ensure stability of
value, since demand may undergo considerable variations.
But in a choice of a money-material, there can be no doubt
that a commodity whose supply is relatively stable, largely
owing to the fact that it is adapted for accumulation, and
that the monetary uses are considerably the most important
of all its uses, presents a greater probability of stability of
value than a commodity of which the supply available for
surrent use is subject to extreme fluctuations.
The demand for money-material, to provide a means of
exchange, is subject to a good deal of modification through
the use of substitutes for, or representatives of, money for
this purpose. Such substitutes are bank-notes or other
paper-money, cheques and bills of exchange, and various
arrangements by which book-entries, on the credit or debit
side of an account, obviate the actual handling of either
money or any concrete representative of money, Banknotes,
 which simply take the place of coin held in a bank,
and are used merely for convenience, do not economise
metallic money beyond what is implied in reducing the
wear and tear of metal. But, as will be seen in the next
chapter, most systems of bank-note issue permit the circulation
 of paper exceeding in face-value the metal which is