If we reject this hypothesis, it will then be allowable to introduce into thermodynamics laws previously excluded, and it will be possible to construct, as M.Duhem has done, a much more comprehensive theory.
The ideas of M.Duhem have been illustrated by remarkable experimental work.

M.Marchis, for example, guided by these ideas, has studied the permanent modifications produced in glass by an oscillation of temperature.

These modifications, which may be called phenomena of the hysteresis of dilatation, may be followed in very appreciable fashion by means of a glass thermometer.

The general results are quite in accord with the previsions of M.Duhem.

M.Lenoble in researches on the traction of metallic wires, and M.Chevalier in experiments on the permanent variations of the electrical resistance of wires of an alloy of platinum and silver when submitted to periodical variations of temperature, have likewise afforded verifications of the theory propounded by M.Duhem.
In this theory, the representative system is considered dependent on the temperature of one or several other variables, such as, for example, a chemical variable.