76 ON THE POWER OF FLUIDS TO CONDUCT HEAT. 



3. The glafs it- 3d. The conducting power of the glafsjar. But as glafs is 

 duct^piobaM known to be a ver V Dad conductor of heat, it can produce no 

 little. material effect in thefe experiments : for which reafon Count 



Rum ford does not appreciate the third caufe. 

 Count Rumford With refpect to the operation of the firfl caufe, it will gc~ 

 that a^old fluid nera fy ^ e ^ppofed that cold water rifing into warmer and re- 

 nting into a maining with it, the heat is impaired, and the two reduced to 

 warmer can cool a common temperalure. But Count Rumford does.not admit 

 of this communication ; he maintains, that the two ftill retain 

 their proper (hare of heat, notwithstanding they are mixed 

 together. This hypothecs of his is of no peculiar confequence 

 as far as refpecls the effect of the internal motion : for the tern* 

 perature indicated by a thermometer immerfed in an equal 

 mixture of water at 32° and 53°, would be the fame as if the 

 water was uniformly of the temperature 42£". But it has 

 whence it would material confequences in other refpects ; for, if it be admitted, 



follow that heat it annihilates the ftcond caufe abovementioned, and it would 

 cannot by trani- _ ,. . ~ " , . ;. ! , 



miffion down- follow that warm water being put upon cold water above the 



wards throw temperature of 42f°, the heat could not in any degree be pro- 



^ 2 io # pagated downwards, unlefs by agitation, and even then, upon 



fubiiding, the warm part ought to rife to the top, and the 



cold fall to the bottom. 

 He has not Thefe pofitions are fo manifeffly contradictory to common 



experiment. * °P m * on * tnat tne y cann °t De received without proof. But 



Count Rumford has not given us a tingle experiment to prove 



them. It feemed necetfary therefore, to clear up this point by 



direct experiments. 



Experiment 1. 

 Examination by Took a large tumbler glafs, 3 \ inches diameter, and five 



wat P "'oured 0t indieS dee P> and fiIied lt half Wa ^ with Water ° f 51 °' then 

 -upon cold air in gently filled up the reft by means of a fmall fyphon, with wa. 

 ag! a fsveflel,the terof g8 o. a thermometer, with its bulb and ftem detached 

 dually cooled, from the frame, being previoufly immerfed to the bottom, 

 and the lower The temperatures at the top and middle were had by gently 

 immerfing the bulb of another thermometer into the water. 



Time 





