ON THE POWER OF FLUIDS TO CONDUCT HEAT. 75 



IV. 



Experiments and Obfervations or the Poiver of Fluids to conduct 

 Heat ; with Reference to Count Rumford's Seventh Ejfay on the 

 fame Subjecl, By John Dalton, 



(Concluded from Page 58.) 



vOUNT Rumford's principal experiments ate thofe in short recapitu - 



which a cake of ice was confined on the bottom of a cylin- , * t,on / . of Coun t 

 t • i t r • r i • »• i i • » .Rumfordsex* 



dncalglais jar, of 4.7 inches in diameter, and 14- high, and per iment of ice 



water poured upon it of different temperatures fuffering it to at the bottom of 



ftand, without agitation. He found that about 6lb of boiling 



hot water melted little more ice than as much water of 41 9 ; 



and that by making fuch allowances as the experiments feemed 



to warrant for deductions when hot water was ufed, water of 



41 9 , or 9° above the freezing point, melted quite as much, 



and often more, than the hot water : From which he infers, 



that water, and by analogy all other fluids, do not tranfmit 



heat in the manner that folids do, but circulate it folely by the 



internal motion of their particles. 



The exiftence of this internal motion he has proved de- The internal 

 cidedly ; that water of a certain temperature being of the great- m ° tlon or circu " 

 eft denfity, will always take the loiveft place, and water either 

 warmer or colder than that degree will afcend. This degree 

 of greateft condenfation he takes on the authority of others at 

 40° ; it appears however from the experiment related above, 

 to be ftill more favourable to his pofition, namely 42^° : and 

 that water of 32° muft afcend till it comes to water of 53% if 

 it be not cooled in its progrefs, which circumftance he admits. 



Upon confidering the fa£ts related in his experiments there- Confideratlon of 

 fore, there are three caufes which fuggeft themfelves as con- thcfa ^ S! 

 fpiring to circulate and diffufe the heat, by which the ice is 

 melted. 



lft. The internal motion of the liquid, by which water of »• Cold water at 

 32°, incumbent upon the ice, is perpetually afcending into *S^f #!• 

 warmer region of 53°, and warmer water of 42f defcendingand warmer of 

 to take its place. tH* defcends. 



2d. The proper condu&ing power of the liquid indepen-2. The fluid it- 

 dent of internal motion. felf ma y con - 



, _, dutt. 

 3d. To* 



