抄録
Physics textbooks show Joule's paddle-wheel equipment in 1850 in relation to the law of conservation of energy, but describe nothing about the background of his experiments. Joule had made many kinds of experiments to determine mechanical equivalent of heat for a long period from 1843 to 1878. Unfortunately, academic society had not appreciated his early studies, because the concept of calorique had still prevailed in the middle of 19c. Even after clear evidence was presented, it takes a long time for the society to recognize a new scientific knowledge. This is a social nature of science, which should be emphasized in scientific education.
