Of WATER by HEAT. 395 



but extremely (lowly, by reafon that fluids, as Count Rumford 

 taught us, are exceflively bad conductors of heat, and fo very 



flowly, 



In experiments of this nature, the difficulty is to prevent the conveyance of ca- 

 loric by the fides of the veffel. I attempted, and, I think, I fucceeded, in over- 

 coming this difficulty, by encircling the larger veffel, at a height exa&ly corre- 

 fponding with that of the furface of the fluid within, with a gutter or channel 

 about half an inch in depth ; and by caufing a ftxeam of cold water to flow con- 

 ftantly through a fyphon into this gutter, while from the oppofite fide it ran off by 

 a fmall fpout. 



The water was feveral degrees colder than the fubjedr, of the experiment ; and 

 keeping cool the portion of the veffel with which it was in contact, it intercepted 

 the heat that would otherwife have travelled by this route to the bottom. 



For mercury I had recourfe to veffels of glafs. 



In all the experiments a thermometer bore teftimony that the caloric defcended 

 from the furface to the bottom of the fluid, and demonftrated, at leaft to my con- 

 vi&ion, that fluids can conduct heat. 



The progrefs of the heat, however, was very flow, and attefted the important 

 faft, for which we ought to be thankful to the Count, — That fluids are very bad 

 conductors. 



The fecond fet of experiments was calculated to examine, in a very different 

 manner, the pofition, That all interchange and communication of heat between the 

 particles of fluids is impoffible. 



When a hot and a cold fluid are mixed together and well agitated, very foon 

 an uniform temperature is produced. This equality mult proceed either from a 

 communication of heat from the warmer to the colder fluid, agreeably to the com- 

 mon opinion, or from a perfect intermixture of hot and cold particles, according to 

 the notion of Count Rumford. To which caufe it ought to be attributed, I con- 

 ceived I might difcover, by afcertaining whether, after fuch an intermixture, any 

 feparation of the hot and cold portions took place. If the equilibrium of tempe- 

 rature be owing to intermixture without interchange of caloric, the hotter parti- 

 cles, as foon as the agitation ceafes, ought, by reafon of their greater rarity, to ac- 

 cumulate, to a certain degree, at the furface, and there exhibit a temperature 

 above the common one. 



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

 nearly ice-cold, in a ftoppered glafs jar, I fhook them well for a fhort time. 



I th'.:n noticed the refulting temperature, and railing the ball of the thermo- 

 meter towards the furface, I had an opportunity of obferving, that it never rofe 



the 



