396 On the CONTRACTION 



ilowly, that the caloric entered from the atmofphere with fuffi- 

 cient quicknefs to prevent any depreflion of temperature below 

 the 39th degree. 



This experiment, I may conclude with remarking, is very 

 well calculated to exhibit the error of the popular opinion, that 

 " heat has a tendency to afcend." 



Experiment 



the fmalleft portion of a degree above the common temperature which had been 

 eftablifhed. 



I next made a fimilar experiment with alcohol, felecting it on account of its re- 

 markable dilatability. I fiiook well, for half a minute, a mixture of equal parts of 

 alcohol at temperature 40 and at temperature 170 . The refulting temperature 

 of the mafs was 104*. 



Now, if this was a mixture of particles at 40 and at 170% as the difference of 

 fpecific gravity between the fluid at thefe temperatures is very confiderable, fome 

 feparation of the warmer and lighter particles from the others, ought, I conceive, 

 to have taken place. The temperature of the top, however, never indicated the 

 arrival of warmer particles. It never afcended above the point of equilibrium. 



From thefe experiments I concluded, that the uniformity of temperature was 

 eftablifhed by an actual communication and interchange of heat between the par- 

 ticles. 



It may not, however, be improper to ftate, that Count Rumford, with whom 

 feveral years ago I had the pleafure of converfing upon this fubject, alleged, that 

 the intermixture might be fo complete as to prevent any feparation whatever. 



If it be a property effential to fluidity, that heat cannot pafs from one particle 

 to another, the particles of different fluids ought to be equally incapable of impart- 

 ing caloric mutually to each other. Unfortunately, however, for the fpeculation, 

 the caloric is fo communicated. Though, a priori, I entertained no doubts re- 

 fpecting the refult of the experiment, I poured a quantity of olive oil which had 

 been heated by immerfion in a veflel of boiling water for half an hour, upon an 

 equal volume of water of 38 , and agitated the mixture, by fhaking for a quarter 

 of a minute. The common temperature produced was 78 , and the heat had gone 

 from the oil into the water ; for when the fluids feparated, and had arranged them- 

 felves according to their fpecific gravity, both of them had the fame temperature 

 of 78°. 



The experiments of the two defcriptions now recorded, left on my mind little 

 doubt that the Count had overftrained his conclufions. 



