Noii'Cctidul^orj of Heat: Water, Oil, Mercury ^ Air, Sieam, P/ame. i6t 



A folid cylinder of wrought iron l^ inch in diameter, and 12 inches long, provided with 

 a hollow cylindrical fheath of thick paper, was heated to the temperature of 210 degrees in 

 boiling water, and, being fuddenly introduced into its fheath, was fufpcnded from the ceil- 

 ing of the room, and very gradually let down into the oil, until the middle of the flat fur- 

 face jof the hot iron, which was diretflly above the point of the conical proje£lion of ice,, 

 was diftant from it only 2-ioths of an inch. The end of the (heath defcended i-ioth of 

 an inch lower than the end of the hot metallic cylinder. The ice was perfeflly vifibic 

 through the oil in every ftage of this experiment. How long the metallic cylinder was 

 kept immerfed in the oil is not fuid, but the time was no doubt fufficient to fatisfy the 

 Count that heat is not propagated downwards through tliis fluid. The ice was not in the 

 fmalleft degree diminiftied, or otherwife afFe(Sed, by the vicinity of the hot iron. 



A fimilar experiment was made with a frefti cake of ice in the fame jar, but with ice- 

 cold mercury covering the cake to the height of about an inch. The furfacc of the mercury 

 in the jar was cleaned with blotting paper, after which the whole was fufFered to remain 

 quiet for about an hour, when the hot cylinder of iron was very carefully introduced, and 

 fufi'ered to remain feveral minutes at the diftance of a quarter of an inch from the point of 

 the conical proje£tion of ice. 



In this as well as in the other experiment, the cylindrical fheath was made to projeft 

 i-ioth of an inch below the bafe of the iron, for the purpofe of diminifhing the internal 

 motions of the fluid. 



In this experiment alfo the ice remained unchanged. In order to fhew whether the ice 

 V/ere really in the flate of melting with the leaft poffible addition of heat, the Count touched 

 it with his finger beneath the mercury ; and he found that this operation could not be f« 

 fueedily performed, but that figns of water having been produced became apparent on the 

 clean and bright furface of the mercury. 



From the refults of thefe experimental invefligation«, it appears to our author that water, 

 oil, and mercury, are perfect non-condu£lors of heat ; and that when either of thefe fub- 

 ftances takes the form of a fluid, all interchange and communication of heat among its 

 particles, or from one of them to the other dirc£Hy, become from that moment abfolutely 

 imf,oJfib!e * . In the Philofophical Tranfaflions for 1792, the Count has fhewn the extreme 

 imperfe£lion of the conducting power of air, and in his Sixth Eflay he has fhewn how much 

 reafon there is to conclude that the particles of fleam and of flame are in the fame predica- 

 ment : From all which circumflances he is difpofed to conclude, that it is common to all 

 fluid', and even efTential to fluidity, that they fhall not immediately or directly condu£l heat 

 from particle to particle. 



Thi^ important circumflance was applied by our author, in the Philofophical Tranfaftions 

 above referred to, to account for the warmth of natural and artificial clothing, and of 

 ("now, as well as to expUin various phenomena of winds. And in his Sixth Eflay he 

 availed himfclf of the non-condu£ting power of fteam and of flame, to explain the efi^6ls 

 of the blow-pipe, and inveftigatc the mofl advantageous forms for boilers. And, lafliy, 



• Oa the abfolute impoffibility of the tranfition of heat through fluids at reft, fee the note in our Journal, 

 1.191, It may however be obferved, that moft of the Count's conclufioas will be- praftically true j thatisto 

 fey, with regard to fuch terms of time as liis experiments juftify. N, 



Vol. II,— July 1798. Y In 



