Mariotte's law

For example, Boyle’s law, which links a gas’s pressure and volume, is often known in France as Mariotte’s law, after seventeenth century physicist Edme Mariotte, who discovered it independently of Anglo-Irish Robert Boyle.

Boyle’s law in English-speaking countries is the same thing as Mariotte’s Law in French-speaking countries.

The relation between the temperature, pressure, and weight of steam is not quite proportional to the volume, because steam is not a perfect gas, and does not, therefore, strictly follow Mariotte’s law.

It is because of this internal work that the steam in expanding does not strictly follow Mariotte’s law.

The usual manner of testing the expansion curve of a diagram is to compare it with a curve representing Mariotte’s law for the expansion of a perfect gas.