J §fi ON THE PASSAGE OF HEAT THROUGH FLUIDS. 



lion, that they conduct caloric in a very imperfe<5t degree, 

 feut the experi- From a feries of experiments which I have undertaken on this 

 decide theouef- f llD J e &> 1 nav ^ been convinced, that inveftigations refpecting 

 tion aboundwith it are liable to fources of error more important, and more dif- 

 ficulties. fi cu j t t0 ^ e avo i^ cc [ t | mn m ight a priori be fuppofed, and that 

 we have no experiments fufhciently unobjectionable to decide 

 the queftion. The obfervations I fliall have to offer in the 

 following memoir, will I truft juflify thefe aflertions. 

 Communication When caloric is communicated to the furface of any folid 

 foJids- r ° US fubuance, the temperature of the whole mafs is increafed with 

 more or lvl's celerity, and becomes uniform. In this cafe the 

 caloric paffes from one particle of the folid to another, and is 

 and fluids. thus equally diftributed through the whole. When caloric is 

 communicated to a mafs of fluid, its temperature is likewife 

 uniformly increafed, and in this cafe alfo it was fuppofed, that 

 the caloric is tranfmitted through the fluid, as in the former 

 example through the folid. Count Rumford denies the poffi- 

 bility of fuch a tranfmiffion, and conceives the change of tem- 

 perature in the fluid to be produced in another mode. 

 Circulation of When any portion of a fluid is heated it muft neceffarily be 

 ui s rom eat * expanded, its fpecific gravity muft be diminifhed, and from its 

 mobility it mufl change its place. If therefore caloric be com- 

 municated through a folid furface to a fluid, the portion of 

 fluid immediately in contact with the folid, when heated, will 

 acquire a fpecific gravity different from that of the mafs; if 

 the caloric is communicated from beneath, the heated portion 

 of fluid muft afcend, its place will be occupied by another 

 portion, and thus the whole mafs will be fucceffively brought 

 into contact with the heated furface, and will have its tem- 

 perature increafed. It is in this mode only according to 

 Count Rumford, that the temperature of fluids can be changed. 

 They can receive caloric from any folid matter with which 

 they are in contact, but the healed portion communicates no 

 part of its caloric to the reft of the mafs, and the change of 

 temperature which the whole fuffers is owing folely to the 

 motions of its parts. 

 The circulation That it is in a great meafure owing to this caufe, has been 

 does not abfo- clearly demonftrated by Count Rumford's experiments. He 



Counfso* inion. !ias mewn > tllat when heat is a PP lied to a fluid, motions of its 

 parts take place, and that whatever retards or obftrucls thefe 

 motions, diminifhes the celerity with which the temperature 



