THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



SUPPLEMENT to VOL. III. FOURTH SERIES. 



LXIX. On the Heat disengaged in Chemical Combinations. 

 By James Prescott Joule, F.R.S. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



THE following memoir was communicated to the French 

 Academy several years ago*, in order to compete for the 

 prize offered for the best essay on the heat of chemical combi- 

 nations. Owing to my not having been aware of the regulations 

 to- be observed by the competitors, and to the delay in procuring 

 a good translation, my paper was deemed ineligible, but was 

 referred to the Commission appointed to examine the memoirs 

 presented on the same subject. The time has now arrived when 

 I feel that I ought not to delay communicating the results of a 

 laborious investigation to the scientific world, and I therefore 

 transmit to you an exact copy of the paper from which the 

 French translation, now in the possession of the Academy of 

 Sciences, was made. The necessity of making no alterations 

 whatever in the paper has prevented me from citing additional 

 authorities, and making sundry small corrections which have 

 occurred to me since it was written. I will therefore avail my- 

 self of the opportunity of making a few prefatory observations. 



I would remark, in the first place, that the laws of the disen- 

 gagement of heat by voltaic electricity received, nearly at the 

 same time that the experiments contained in my paper were 

 made, a new confirmation and important developments by the 

 researches of Professor J. D. Botto of Turin. This valuable 

 contribution to physical science will be found in the Memoirs of 

 the Academy of Sciences of Turin, 2nd series, vol. viii. In the 

 Bulletin des Sciences of the Berlin Academy for the 25th of No- 

 vember 1848, will also be found an able memoir on the same 

 subject by Professor Poggendorff. 



* See the Comptes Rendus for February 9, 1846. 

 Phil. Mag. S. 4. No. 21. Suppl. Vol. 3. 2 I 



