the 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JUNE 1868. 



XLVII. On the Second Fundamental Theorem of the Mechanical 

 Theory of Heat ; a Lecture delivered before the Forty-fast 

 Meeting of the German Scientific Association, at Frankfort on 

 the Maine, September 23, 1867. By R. Clausius, Professor 

 of Physics in the University ofWurzburg*. 



HAVING been honoured with a requisition to deliver a dis- 

 course to the present general meeting of the Association, 

 I have felt it incumbent upon me to choose as my theme, not 

 the result of any special investigation, but some subject of wide 

 application and general interest. I will therefore take the liberty 

 of giving, as briefly and in as easily intelligible a form as possible, 

 an account of the theorem known as the Second Fundamental 

 Theorem of the Mechanical Theory of Heat, which forms one of 

 the two great principles whereon this whole theory is based. It 

 is obvious that it is impossible for me upon the present occasion 

 to present this theorem in a mathematical form, or to give a 

 strict proof of its truth, and to follow out individually its nume- 

 rous applications ; all 1 can do is to place its meaning and its 

 connexion with the first fundamental theorem of the mechanical 

 theory of heat in a clear light, and perhaps to illustrate by a few 

 examples the conclusions which may be deduced from it. 



It is well known that rather more than twenty years ago, fol- 

 lowing upon the isolated and more general statements of various 

 earlier authors, Mayer of Heilbronn distinctly asserted, and 

 Joule of Manchester proved to demonstration by his experimental 

 investigations, that there exists between mechanical work and 



* Translated from a pamphlet communicated by the Author. 

 Phil. Mag. S. 4. Vol. 35. No. 239. June 1868. 2 E 



