which will have cost us the trouble of production. From which we see
that the exchange is between efforts, [time and] labor. It is
certainly not for hydrogen gas that I pay, for this is everywhere at
my disposal, but for the work that it has been necessary to accomplish
in order to disengage it; work which I have been spared, and which I
must refund. If I am told that there are other things to pay for, as
expense, materials, apparatus, I answer, that still in these things it
is the work that I pay for. The price of the coal employed is only the
representation of the [time and] labor necessary to dig and transport
it.

We do not pay for the light of the sun, because nature alone gives it
to us. But we pay for the light of gas, tallow, oil, wax, because here
is labor to be remunerated;--and remark, that it is so entirely [time
and] labor and not utility to which remuneration is proportioned, that
it may well happen that one of these means of lighting, while it may
be much more effective than another, may still cost less. To cause
this, it is only necessary that less [time and] human labor should be
required to furnish it.

When the water-boat comes to supply my ship, were I to pay in
proportion to the _absolute utility_ of the water, my whole fortune
would not be sufficient. But I pay only for the trouble taken. If more
is required, I can get another boat to furnish it, or finally go and
get it myself. The water itself is not the subject of the bargain, but
the labor required to obtain the water. This point of view is so
important, and the consequences that I am going to draw from it so
clear, as regards the freedom of international exchanges, that I will
still elucidate my idea by a few more examples.