The sum of the weights of the mercury and the gas which were produced by heating the calcined mercury was equal to the weight of the calcined mercury; and the weight of the gas produced by heating the calcined mercury was equal to the weight of the portion of the air which had disappeared during the formation of the calcined mercury.

This experiment proved that the calcination of mercury in the air consists in the combination of a constituent of the air with the mercury.Fig.XVII.

(reduced from an illustration in Lavoisier's Memoir) represents the apparatus used by Lavoisier.

Mayow's supposition was confirmed.
[Illustration: FIG.

XVII.] Lavoisier made many more experiments on combustion, and proved that in every case the component of the atmosphere which he had named oxygen combined with the substance, or with some part of the substance, which was burned.