Page:Popular Science Monthly Volume 73.djvu/105

Rh The local press would at first have nothing to do with it. One paper refused to give even a notice of it. The Manchester Courier, after long debate, published the address in full. In June, 1847, the subject was presented before the British Association meeting at Oxford. The chairman suggested that the author be brief. No discussion was invited. In a moment the section would have passed on to other matters without giving the new ideas any consideration, if a young man had not risen from his seat and by his intelligent observations created a lively interest in the new theory. The young man was William Thomson, now better known as Lord Kelvin. The result was that the paper caused a great sensation. Joule had attracted the attention of scientific men. After the meeting Joule and Thomson discussed the subject further and the latter obtained ideas he had never had before.

Joule experimented on the mechanical equivalent of heat for about forty years. By magneto-electric currents he got in 1843 the value of 460 kilogrammeters as the equivalent of the large French calorie. By the friction of water in tubes he obtained 424.9; by the compression of air, in 1845, 443.8; by the friction of water he obtained, in 1845, 488.3; 'in 1847, 428.9; in 1850, 423; in 1878, 423.

Comparing Joule with Mayer, it will probably be admitted nowadays that Joule stands first as an experimentalist, while Mayer towers above Joule as a generalizer, as a physical philosopher.

The same year, 1847, in which Joule announced his views on energy before the British Association, Helmholtz, a youth of 26, read before the Physical Society in Berlin a *paper on the same subject, entitled, "Die Erhaltung der Kraft." It was at first pronounced a fantastic speculation. The editor of Poggendorff's Annalen, who in 1841 declined Mayer's paper, rejected Helmholtz's also. As Joule was supported by William Thomson, so-Helmholtz was defended by his fellow student Du Bois-Beymond, and by the mathematician C. G. J. Jacobi. Helmholtz's paper was published in pamphlet form in 1847. For a time it attracted little notice, but in 1853 some parts in it were vigorously attacked by Clausius in Poggendorff's Annalen. Later it subjected its author to bitter attacks from Eugen Karl Dühring and others, who accused him of being a dishonest borrower from his forerunner, Robert Mayer. In a publication of 1898, issued in Berlin, Dr. Thomas Gross does not quite accuse Helmholtz of plagiarism, but claims that Helmholtz did all he could to discredit Mayer. In my judgment both Dühring and Gross failed to establish their contentions. In the absence of clear evidence to the contrary we prefer to accept Helmholtz's own statement, as given in one of his lectures. Helmholtz says in one place, "The first who saw truly the general law here