Prof. Tyndall, although the English champion of Mayer's claims, did ample justice to his own countryman, as the following passage shows: "It is to Mr. Joule, of Manchester, that we are almost wholly indebted for the experimental treatment of this subject. With his mind firmly fixed on a principle, and undismayed by the coolness with which his first labors appear to have been received, he persisted for years in his attempts to prove the invariability of the relation between heat and ordinary mechanical force. He placed water in a suitable vessel, agitated it by paddles moved by measurable forces, and determined the elevation of temperature; he did the same with mercury and sperm-oil. He caused disks of cast-iron to rotate against each other, and measured the heat produced by their friction. He urged water through capillary tubes, and measured the heat thus generated. The results of his experiments leave no doubt upon the mind that, under all circumstances, the absolute amount of heat produced by a definite amount of mechanical force is fixed and invariable."
For this great scientific achievement the Royal Medal of the Royal Society was awarded to Mr. Joule in 1852; and eight years later, when men of science began more fully to apprehend the great value of the discovery, he was presented also with the Copley Medal of the Royal Society. On that occasion, Sir Edward Sabine, the president, alluding to the former award, used the following words: "Both awards refer to the same experiments, and are substantially for the same great step in natural philosophy. You are all aware that a great principle has been added to the sum of human knowledge—one fruitful in consequences in a thousand ways, and which, being accepted among undisputed truths, is now embodied, without question, alike in the most wide-ranging speculations and the most matter-of-fact practice. The award of two medals for the same researches is an exceedingly rare proceeding in our society, and rightly so. The council have, on this occasion, desired to mark by it, in the most emphatic matter, their sense of the special and original character and high desert of Mr. Joule's discovery. No words of mine could add to the value of the award."
Dr. Joule has figured but little in the fields of popular science, having only given a few lectures to the people in Manchester, and published no book, as we are aware, of any kind. But his contributions to scientific periodicals and the transactions of learned societies are very numerous, and give the results of prolonged and incessant original investigations, extending through many years. He became a Fellow of the Royal Society in 1850, received the degree of B. C. L. from Oxford, of LL. D. from the Universities both of Dublin and of Edinburgh, is a corresponding member of the Institute of France, and was President-elect of the British Association for the Advancement of Science, which met at Bradford last year.
