©N FLUIDS AS CONDUCTORS OF HEAT. .137 



win vary according to the manner in which the temperature is ^[fj' difference of 

 preferved in the liquids. If the vefl'el has a non-condu6iing temperature is 

 covering, the heat will be retained, and a greater quantity will ^°!^ 1^°^!^^ 

 be communicated than if it had been allowed to pafs into fur- caufesof its 

 rounding bodies — But when the difference of the temperature communication. 



r , ,. . , . r -1 • 1 • 1 ^' Rumford s 



of the liquid is not conuderable, as m the experiment in which experiments re- 

 water at 16° was employed, it is more advantageous toaiig- quire no new law 

 .1 rr r^ 1 n ■ r ^i x- I i to explain thenw 



ment the enect ovvmg to the tranflation or the particles, by 



cooling all the cylinder, than to preferve that which is owing 

 to the fimple communication of caloric. It appears to me that 

 this explanation naturally flows from the known properties of 

 fluids, and that Rumford's obfervations do not lead us to new 

 inductions 



It muft be remarked that by feparating theefl^edl which took Additional re- 

 place at the firft, when a confiderable difference in the tern- '"^ * 

 perature could occafion a quick communication, he only ob- 

 ferved that which was produced when there were but very * 

 flight differences between fucceflive flrataof the liquid and the 

 ice itfelf: now, when there is but a fmall difference of fatu- 

 ration, either between chemical combinations, or between the 

 temperatures^ the equilibrium is eftabliflied very flowly, and it 

 becomes difficult to appreciate the effeds. 



The experiments which Rumford made by plunging a fmall Experiments 



1- 1 /- • . . . . / ■ 7 ,V- • ,■ with mercury 



cylinder ol iron, heated to the degree of the ebullition of and heated iron. 



wafer, into water and mercury ffanding over a fmall piece of 

 ice, without producing its liquefaction, only prove that when 

 two bodies differ but little in their temperature, the equilibri- 

 um is eftabliflied with difficulty ; for it mufl be obferved that the 

 iron, which had but a little fpecific heat, and is a good con- 

 ductor, muff have loft the grealeff part of its heat rapidly, in 

 that part of the liquid which it paffed gently through, and ne- 

 verthelefs have raifed that of the liquid but little, or even that 

 of the mercury, confidering the mafs of it. 



But in thele experiments of Rumford I find proofs of the Other fa^^s to 



property which he denies to liquids. ^^"^ *^^' ^^'*^* 



n T 1 1 I • . • 1 T I . .are proper con- 



llt. In all the experiments which I have quoted, except in dudors. 



thofe made with the heated cylinder of iron, the liquefaftion 



of the ice took place in a confiderable degree, and each part 



liquified fuppofes a quantity of heat which would have raifed 



an equal weight of water from the term of congelation to 75 



degrees of the centigrade thermometer. 



2d. He 



