Propagation of Heat in Liquids. 277 



by the ascending currents which are formed in the liquid 

 in consequence of the heat which it receives from the 

 hot body. 



The existence of these currents in certain cases has 

 been known a long time, but philosophers have not been 

 sufficiently attentive to the many curious phenomena 

 that depend upon them. It has not even been suspected 

 with what extreme slowness heat passes in fluids, from 

 particle to particle, de proche en proche, in cases where 

 the effects of such communication become sensible. 



For some time after I had engaged in this interesting 

 inquiry, I conceived that this kind of communication 

 was absolutely impossible in all cases ; but a more atten- 

 tive examination of the phenomena has convinced me 

 that this conclusion was too hasty. As early as the be- 

 ginning of 1800, in a note published in the third edition 

 of my Seventh Essay, I announced a conjecture that the 

 non-conducting power of fluids might perhaps depend 

 solely on the extreme mobility of their particles ; and it 

 is certain, if this conjecture is well founded, liquids must 

 necessarily become conductors of heat (though very im- 

 perfect ones) in all cases where this mobility of their 

 particles is destroyed, as well as in these rare but yet 

 possible cases, where a change of temperature can take 

 place in a liquid without giving its particles any ten- 

 dency to move, or to be moved out of their places. 



The unequivocal results of a great many experiments 

 have shown, that in ordinary cases, and perhaps in all 

 cases where heat is propagated in considerable masses of 

 fluids, its distribution is accomplished precisely in the 

 manner that the new theory supposes, that is to say, by 

 currents. And it is certain that the knowledge of that 

 fact has enabled us to explain in a satisfactory manner 



