5^]0 ACCOUNT OF A CURIOUS PHENOMENON. 



danger of being invalidated by conclufions drawn from partial 



and imperfe6l experiments, and particularly from fuch as are 



allowed on all hands to be extremely delicate. 



Heat of the fides In all our attempts to caufe heat to defcend in liquids, the 



of the veflel, ^^^^ unavoidably communicated to the fides of the containing 



and defcending -^ i r « i r w 



current in a vef- vetTel, muft occafion great uncertainty with refpect to the remits 

 £el of ice. ^f tj^e experiment ; and, when that veffel is conftru6led of ice, 



the flowing down of the water refulting from the thawing of 

 that ice, will caufe motions in the liquid, and confequently in- 

 accuracies of ftill greater moment, as I have found from my 

 own experience; and, when thermometers immerfed in a liquid, 

 atafmallditlance below its furface, acquire heat, inconfequence 

 of a hot body being applied to the furface of the liquid, that 

 event is no decifive proof that the heat acquired by the thermo- 

 meter is communicated by the fluid, from above, downwards, 

 from molecule to molecule, de proche en proche; io far from 

 being fo, it is not even a proof that it is from the fluid that the 

 thermometer receives the heat which it acquires; for it is poffi- 

 ble, for aught we know to the contrary, that it may be occa- 

 fioned by the radiation of the hot body placed at the furface of 

 the fluid. 

 Reference to the In the experiments of which I have given an account, in my 



experiments of -gihy on the Propagation of Heat in Fluids, great mafles, 

 boiling water •' , . . , r i i- i , . i 



landing over many pounds m weight, ot boiling hot water, were made to 



ice. repofe for a long time (three hours) on a cake of ice, without 



melting but a very fmall portion of it; and, on repeating 

 the experiment with an equal quantity of very cold water, 

 (namely, at the temperature of 41® Fahrenheit,) nearly twice 

 as much ice was melted in the fame time. In ihefe experi- 

 ments, the caufes of -uncertainly above mentioned did not 

 exift : and the refults of them were certainly moft flriking. 



The conclufions which naturally flow from thofe refults, have 

 always appeared to me to be fo perfeflly evident and indifputa- 

 ble, as to fland in no need, either of elucidation, or of farther 

 proof. 



If water be a conductor of heat, how did it happen that the 

 heat in the boiling water did not, in three hours, find its way 

 downwards, to the cake of ice, on which i,t repofed, and from 

 which it was feparated only by a ftratum of cold water, half an 

 inch in thicknefs ? 



I vviOa 



