[Pierre Bayen rediscovers the Essays of Jean Rey]

Jean Rey, a physician from The Bugue, a little town near Bergerac, published, in 1630, a book entitled "Essays" in which he explained the increase of the mass of lead, when it was strongly heated, by the fixation of a part of the air. This revolutionary publication was not received by the European scientists, because the Father Mersenne, "the secretary of learned Europe", was not able to repeat his experiments. Between 1774 and 1775, Pierre Bayen, who was a military apothecary, published his Works concerning the "precipitate per se", for us HgO, showing that when this compound was destroyed by heating, it produced a gas, and that the mass of this gas and the mass of the mercury obtained were equal to the mass of the "precipitate per se". He concluded that the phlogiston theory was contradictory with the results of the experiments. When, later on, Lavoisier published his important article on the increase of the mass of steal when it was heated in the air, he "forgot" to cite the Works of Bayen. In January 1775, Pierre Bayen published a letter in which he mentioned that he had discovered an exemplar of Jean Rey's book and explained that this physician of the 17th century had supposed the explanation that had been proved by Lavoisier. Nicolas Gobet then published a new edition of the "Essays" in 1777, but this new edition became itself quite rare. An inscription pencilled on the book kept by the British Museum pretends that all the exemplars Lavoisier could find were destroyed. It is not rigorous to conclude on a single document, especially when it is not signed, but it is sufficient to induce doubt.