198 Mr. Murray on the HercnlaneanMSS, fyc. [Sept. 



ture of a body during the act of combination? This conclusion at 

 Jeast is founded on the strongest analogies, and ought to be 

 followed through all its consequences. 



We are far from pretending that the changes of constitution, 

 which are the result of chemical combinations, have no part in 

 the development of the heat which accompanies them. We mean 

 to say merely that in very energetic combinations this cause 

 produces in general but a very small part of the total effect. 



We cannot pass in silence, in terminating this memoir, another 

 very important application to wbich the exact knowledge of the 

 specific weight of the atoms will lead. If, as we have reason to 

 expect, we succeed by the foregoing considerations to determine 

 this element with accuracy, we may, setting out from the proper 

 densities of bodies, calculate the ratios which exist between the 

 distances of their atoms. But it is easy to see how important it 

 will be in a great many physical theories to be able to establish 

 a comparison between the distances of the particles and certain 

 phenomena, which it is natural to suppose connected with this 

 new element. It is, for example, by examining the question of 

 dilatations under this new point of view that we may expect to 

 arrive at simple laws, at present altogether unknown. Some 

 trials made on the observations of different philosophers, and 

 upon some of our own made with a different object, lead us to 

 consider it as very probable that there exists a simple relation 

 between the dilatability of liquids and the distances of their 

 particles. The fine observations of Gay-Lussac on the identity 

 of the contractions of carburet of sulphur and alcohol, setting 

 out from their respective boiling points, support our opinion ; 

 for these two liquids present this remarkable particularity, that 

 at the temperatures in which they were compared, the distances 

 between their particles are almost exactly the same. But before 

 prosecuting the researches on this subject, it is necessary to 

 elucidate as much as possible the question of specific heats, and 

 to deduce from it all the consequences to which it may lead 

 relative to the knowledge of the constitution of bodies. 



Article V. 



On the Herculanean MSS, fyc. By J. Murray, Esq. 

 (To Dr. Thomson.) 



SIR, London, June 7, 1819. 



There are none who entertain a higher opinion of the talents 

 of Sir H. Davy than myself, but I shall only bend to the autho- 

 rity of great names when my own experience confirms the 

 speculations in which they sometimes wish to indulge. Sir 



6 



