166 On the Contraction of JVater hj Heat. 



us, are excessively bad conductors of heat, and so very 

 slowly, that the caloric entered from the atmosphere with 

 sufficient quickness to prevent any depression of tempera- 

 ture below the 3gth degree. 



This experiment, T may conclude with remarkins;, is 

 very well calculated to exhibit the error of the popular 

 opinion, that " heat has a tendcncv to ascend." 



Experiment IV. 



I took the same tall jar, and stoppii^g the tubulature 

 with a cork, I filled it with water of tenjperature 40", and 

 placed it in a pan. After suspending two thermometers, 

 as in experiment first and second, I poured a mixture of 

 ice and salt into the pan, to the depth of 4-2 inches, the 

 air of the room being 40", as in the last experiment. 



I first tried water, and mixing; this fluid boiling hot, with an equal quanti- 

 ty nearly ice-cold, in a stoppered glass jar, I shook th^m well lor a short 

 time. 



I then noticed the resultiiig temperature, and raising the ball of the ther- 

 mometer towards the surface, I had an opportunity of observinj^, that it 

 never rose the smallest portion of a degree above the common temperature 

 which had been established. 



I next made a similar experiment with alcohol, sdecting it on account of 

 its remarkable dilatabilitv. I shook wtli, for half a minute, a mixture of 

 equal parts of alcohol at temperature •!0'^ and at temperature 170". The re- 

 sulting temperature of the mass was 101". 



Now, if this was a mixture of particles at 40" and at 170", as tlie difference 

 of specific gravity between the fluid at these temperatures is very consider- 

 able, some separation of the warmer and Ii<:;hter partic'es from the others, 

 ought, I conceive, to have taken place. The temperature of the top, how- 

 ever, never indicated the arrival of warmer particles. It never ascended 

 above the point of equilibrium. 



From these experiments I concluded, that the ijnifnrmity of temperature 

 was establis-htd by an actual communication and interchange of heat be- 

 tween the particles. 



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

 whom several years ago i had the pler.f.ure of conversing upon this subject, 

 alleged, that the intermixture migly be so complete as to prevent any sepa- 

 ration whatever. 



If it be a property essential to fluidity, that heat cannot pass from one 

 particle to another, the particles of different fluids ought to be equally in- 

 capable of imparting caloric mutually to each otlier. Lnifortunately, how- 

 ever, for the speculation, the caloric is so conimuuicated. Though, a priori, 

 I entertained no doubts respecting the result of the experiment, I poured a 

 quantity of olive oil which had been heated by immersion in a vessel of 

 boiling w.iter for half an hour, upon an equal volume of water of 38", and 

 agitated the mixture, by shaking for a quarter of a minute. The com- 

 mon temperatu' e produced was 7S", and the heat had gone from the oil 

 into the water ; for when the fluids separated, and had arranged themselves 

 according to their specific gravity, both of them had the same temperature of 

 78". 



The experiments of the two descriptions now recoided, left on my mind 

 little doubt that the Count had overstrained his conclusions. 



Eleven 



