XX.
RUDOLF JULIUS EMANUEL CLAUSIUS.
[Proceedings of the American Academy, new series, vol. xvi, pp. 458–465, 1889.]
Rudolf Julius Emanuel Clausius was born at Cöslin in Pomerania, January 2, 1822. His studies, after 1840, were pursued at Berlin, where he became Privat-docent in the University, and Instructor in Physics in the School of Artillery. He was Professor of Physics at Zürich in the Polytechnicum (1855–67) and in the University (1857–67), at Würzburg (1867–69), and finally at Bonn (1869–88), where he died on the 24th of August, 1888.
His literary activity commenced in 1847, with the publication of a memoir in Crelle's Journal, "Ueber die Lichtzerstreuung in der Atmosphäre, und über die Intensität des durch die Atmosphäre reflectirten Sonnenlichts."[1] This was immediately followed by other writings relating to the same subject, two of which were subsequently translated from Poggendorff's Annalen[2] for Taylor's Scientific Memoirs. A treatise entitled "Die Lichterscheinungen der Atmosphäre" formed part of Grunert's "Beiträge zur meteorologischen Optik."
An entirely different subject, the elasticity of solids, was discussed in his paper (1849), "Ueber die Veränderungen, welche in den bisher gebräuchlichen Formeln für das Gleichgewicht und die Bewegung fester Körper durch neuere Beobachtungen nothwendig geworden sind."[3]
But it was with questions of quite another order of magnitude that his name was destined to be associated. The fimdamental questions concerning the relation of heat to mechanical effect, which had been raised by Rumford, Carnot, and others, to meet with little response, were now everywhere pressing to the front.
"For more than twelve years," said Regnault in 1853, "I have been engaged in collecting the materials for the solution of this question:—Given a certain quantity of heat, what is, theoretically, the amount of mechanical effect which can be obtained by applying the heat to evaporation, or the expansion of elastic fluids, in the various circumstances which can be realised in practice?"[4] The twenty-first
