For French chemistry the early 1770's were lively years of discovery and controversy. Two neglected areas of research were opened up in 1772 with the publication of the Digressions académiques by Louis-Bernard Guyton de Morveau and with the first knowledge of later British pneumatic chemistry. Guyton's book established the general fact of weight-gain in metals upon calcination, thereby raising the problem of reconciling this gain with simultaneous loss of phlogiston. The spread of pneumatic chemistry, which proceeded rapidly in 1773, stimulated a renewed interest in the nature of air and its part in chemical composition. It was, of course, Antoine Laurent Lavoisier who perceived a relationship between these two developments—one which he believed would revolutionize the current understanding of chemical processes. In 1772 Lavoisier began the series of investigations which culminated in his Opuscules physiques et chimiques (1774), in which he demonstrated that weight-gain in both calcination and combustion is correlated with absorption of an equal weight of air.