It was not, Monsieur, till after I had published in your journal, the second part of my experiments on the calces of mercury, that I became acquainted with Rey's book. I could not mention it in the very short enumeration I then gave of the different opinions on the cause of the increased weight of metallic calces; my fault, involuntary as it was, must be repaired, and to this end, I hasten to do justice to an author, who, by the profoundness of his speculations, has succeeded in assigning the true cause of that increase.

John Rey (1583–1645) (or, in French) Jean Rey, was a physician of Périgord, France who in 1630 published a tract on calcination, or oxidation of metals, after being notified by Brun, an apothecary of Bergerac, France, of Brun's experiments (as early as 1629) on the calcination of tin. Brun had melted 2 pounds six ounces of tin, and after 6 hours the resulting calx weighed seven ounces more than the original tin. More than one hundred and forty years before Antoine Lavoisier, John Rey recognized that in the calcination of lead or tin, part of the air provided an increase in mass to the calcined metal oxide. His work was eclipsed first by the phlogiston theory and then later, by Lavoisier's discoveries disproving the existence of phlogiston. Lavoisier's oxygen theory confirmed Rey's earlier report, of which Lavoisier claimed he was unaware. After the presentation of Lavoisier's 1775 memoir at the Académie des sciences, Pierre Bayen (1725-1798) wrote a letter to Abbé François Rozier, director of the journal Observations sur la Physique, sur l'Histoire naturelle and sur les Arts, to ask him to publish an update notice, recognizing the priority Rey's work.