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exchangeable value. And if that addition were at any time 
sufficiently large to tend to depress the real or labour value, 
the decline would tend to check the production or increase 
the consumption. Of course it is conceivable in the case 
of these commodities, as in that of others, that certain dis- 
coveries might make their production easier, and might, 
therefore, tend to depress their labour value quantitatively. 
This is so improbable in the case of the precious metals, 
however, that it may be treated as a practical impossibility. 
There is not the remotest probability that either of the 
precious metals will ever be obtained more easily than silver 
has been obtained during the last ten years. Yet the real 
or labour value of silver has remained practically unchanged. 
Moreover, a greatly increased production would still be only 
a small percentage on the existing stock, and would, there- 
fore, be not at all likely to perceptibly lower its exchangeable 
value; the saving in the labour cost of production would dis- 
appear in the form of rent or dividends to the owners of the 
particular mines. In the case of other commodities it has 
of course frequently happened that their relative labour 
value in exchange has been lowered by scientific discoveries, 
which have greatly diminished the labour required for their 
production ; but these very labour-saving discoveries tend 
to extend their influence to the production of the general 
mass of commodities, the labour cost of which will sooner 
or later be reduced proportionately, and the general relations 
will thus tend to remain steady. But in selecting com- 
modities as the permanent representatives of the real or 
labour standard of value, it is obviously desirable to select 
those of which the labour cost of production is least likely 
to be depreciated by any possible scientific or other dis- 
coveries; and ill the precious metals we have such com- 
modities. 
But while, therefore, we find that the ordinary play of 
