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.

Until fairly recently a common way of doing history of science was to pick up an important strand of contemporary scientific thought and to trace its origin back to the philosophical tangle of the scientific revolution. This approach conveniently by-passed the breakdowns of once useful and pervasive theories, and neglected the long intellectual journeys along devious routes. History of science read like a success story; the pioneers who failed were neither dismissed nor excused; they were simply ignored. The historian knew what he was hunting for and he was careful to limit his search to areas where his quarry was sure to be found. This method, which has been dubbed the precursor-view, stands in contrast—albeit, not in opposition—to the contextual method, which aims at a better understanding of the actual thought-processes of the early scientists. On this second view, history of science must not only account for present theories in the light of past developments, it must also assess old theories in terms of the scientist's conceptual framework, and judge them against the background of the world picture of his age. This may lead the historian down the blind alleys of the past, chasing spurious attempts at explaining the nature of physical reality, but it can clear the ground for a less anachronistic interpretation of the emergence of modern science and the actual process of discovery. History of science acts as a winnowing fork, but we cannot suppose that the discoverer himself always separated the wheat from the chaff, and we must be ever wary of equating the dream with the task.

Research on thermal “black-body” radiation played an essential role in the origin of the quantum theory at the beginning of the twentieth century. This is a well-known fact, but historians of science up to now have not generally recognized that studies of radiant heat were also important in an earlier episode in the development of modern physics: the transition from caloric theory to thermodynamics. During the period 1830–50, many physicists were led by these studies to accept a “wave theory of heat”, although this theory subsequently faded into obscurity.