Abstract

In 1813, two young physicists, François Delaroche and Jacques-Étienne Bérard, published a series of highly influential measurements of the specific heats of a number of common gases. Their results, obtained in answer to a prize competition set by the Institut de France, were accepted as the most accurate then available and they continued to exert a powerful, if diminishing, influence on studies of heat for the next forty years. Among the results obtained by Delaroche and Bérard were two measurements which showed that the specific heat of air decreased when the pressure was raised. This was a new and important experimental result. The ‘effect’ was found to be spurious of course , but in the meantime it was clear endorsement of some of the tenets of the caloric theory of heat. It could be invoked, for example, to explain the rise of temperature of a gas when it was compressed adiabatically. Robert Fox in his study of the rise and fall of the caloric theory has written:Their error, although less than 10 per cent, was to prove one of the most influential in the whole history of the study of heat. Backed by the prestige associated with victory in the Institute's competition, the result quickly became standard and… was to mislead many calorists