145 
economic laws tends to prevent the depreciation of the real 
or labour value of the precious metals in terms of other 
commodities also produced by labour, when we come to 
consider variation in the other direction, that is in the 
direction of appreciation of their value in exchange, we find 
that there is no exchangeable commodity in existence the 
exchangeable value of which is not liable to appreciation 
under the infiuence of physical conditions which are beyond 
the operation of economic laws. This is because, though the 
production of any commodity may be always diminished at 
will by the cessation of labour, there is no commodity which 
can be always increased at will by the continuance of labour. 
“Which of us by taking thought can add a cubit to his 
stature ?” A sudden expansion of demand beyond the possible 
limits of supply in the case of mining products, —or natural 
conditions, such as unfavourable seasons — in the case of agri- 
cultural products — or epidemics, in the case of live stock, may 
cause a rapid rise in exchangeable value, which, as it is beyond 
the control of labour, is practically a divergence from the 
average labour standard of value. Thus, even wheat, the 
most widely cultivable of products and one which, as a 
primary food-stuff, will always be widely cultivated, is liable 
to sudden variations of exchangeable value in accordance 
with the character of the season, and regardless of the quantity 
of labour or extent of land devoted to its production ; so much 
so, that Adam Smith tells us that, though the exchangeable 
value of corn-rents is likely to be most steady from century 
to century, it is likely to vary even more than that of money 
rents from year to year. 
Now in the case of the precious metals we have com- 
modities which, though never likely to permanently 
depreciate in their exchangeable value, and though 
more suitable than any other commodities to fulfil the 
functions of currency and legal tender, have, in common 
