From which we see that the exchange is between troubles, efforts, labors.

It is certainly not for hydrogen gas that I pay, for this is every where 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 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 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.