Joule now tried a third route. He measured the heat generated against the work done in compressing a gas. He obtained a mechanical equivalent of . In many ways, this experiment offered the easiest target for Joule's critics but Joule disposed of the anticipated objections by clever experimentation. Joule read his paper to the Royal Society on 20 June 1844, but his paper was rejected for publication by the Royal Society and he had to be content with publishing in the "Philosophical Magazine" in 1845. In the paper he was forthright in his rejection of the caloric reasoning of Carnot and Émile Clapeyron, a rejection partly theologically driven: