“About eight days ago, I discovered that sulphur, when burned, instead of losing weight, gains weight; that is to say, from one pound of sulphur much more than one pound of vitriolic acid is produced, not counting the moisture gained from the air. Phosphorus presents the same phenomenon. This increase of weight is due to a great quantity of air which becomes fixed during the combustion, and which combines with the vapours. This discovery, which I confirmed by experiments which I regard as decisive, led me to think that what is observed in the combustion of sulphur and phosphorus might likewise take place with respect to all the bodies which augment in weight by combustion and calcination; and I was persuaded that the gain of weight in calces of metals proceeded from the same cause. Experiment fully confirmed my conjectures. I effected the reduction of litharge in closed vessels with Hales’ apparatus, and I observed that at the moment of the passage of the calx into the metallic state, there was a disengagement of air in considerable quantity, and that this air formed a volume at least a thousand times greater than that of the litharge employed. As this discovery appears to me to be one of the most interesting which has been made since the time of Stahl, I thought it expedient to secure to myself the property, by depositing the present note in the hands of the Secretary of the Academy, to remain secret till the period when I shall publish my experiments.” LAVOISIER. “PARIS, _11th November 1772_.” [Illustration: ANTOINE AUGUSTE LAVOISIER.] There is no account in Hales’ work of his reducing litharge in closed vessels. It is to be presumed that Lavoisier heated in a retort a mixture of litharge and charcoal, and that the air which he speaks of was a mixture of oxides of carbon. This account does not inform us of Lavoisier’s views on combustion, but merely shows the date at which he had first obtained what he supposed were results new to science. We recognise that Mayow had anticipated him in this.