Thus appears the idea that energies which exchange with each other and correspond to equal quantities have not the same qualitative value.

Form has its importance, and there are persons who prefer a golden louis to four pieces of five francs.

The principle of Carnot would thus lead us to consider a certain classification of energies, and would show us that, in the transformations possible, these energies always tend to a sort of diminution of quality--that is, to a _degradation_.
It would thus reintroduce an element of differentiation of which it seems very difficult to give a mechanical explanation.

Certain philosophers and physicists see in this fact a reason which condemns _a priori_ all attempts made to give a mechanical explanation of the principle of Carnot.
It is right, however, not to exaggerate the importance that should be attributed to the phrase degraded energy.

If the heat is not equivalent to the work, if heat at 99 deg.