458 RUDOLF JULIUS EMANUEL CLAUSIUS. 



RUDOLF JULIUS EMANUEL CLAUSIUS. 



Rudolf Julius Emanuel Clausius was born at Coslin in 

 Pomerania, Janiiarj 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 Zurich in the Polytechnicum (1855-67) and in the 

 University (1857-67), at Wiirzburg (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 At- 

 mosphiire, und iiber die Intensitat des durch die Atmosphare reflec- 

 tirten Sonnenlichts." * This was immediately followed by other 

 writings relating to the same subject, two of which were subsequently 

 translated from PoggendorfF's Annalen f for Taylor's Scientific Me- 

 moirs. A treatise entitled " Die Lichterscheinungen der Atmos- 

 phiire " formed part of Grunert's " Beitrage zur meteorologischen 

 Optik." 



An entirely different subject, the elasticity of solids, was discussed 

 in his paper, (1849,) " Ueber die Veriiiiderungen, welche in den bisher 

 gebriiuchlichen Formelu fiir das Gleichgewicht und die Bewegung 

 fester Korper durch neuere Beobachtungeu nothwendig geworden 

 sind." t 



But it was with questions of quite another order of magnitude that 

 his name was destined to be associated. The fundamental 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 ques- 

 tion : — 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 realized in practice ?"§ The twenty-first 

 volume of the Memoirs of the Academy of Paris, describing the first 

 part of the magnificent series of researches which the liberality of the 

 French government enabled him to carry out for the solution of this 



* Vol. xxxiv. p. 122, and vol. xxxvi. p. 185. 

 t Vol. Ixxvi. pp. 161 and 188. 

 } Pogg. Ann., vol. Ixxvi. p. 46 (1849). 

 § Comptes Rendus, voL xxxvi. p. 676. 



