ON FLUIDS AS CONDUCTORS OF HEAT. 199 



tion by the appearance of the fun *; ihefe phenomena feem 

 to me to indicate that the elafiic fluids, far from being bad 

 conduftors, on the contrary, receive the temperature of oiher 

 bodies very quickly; for, can it be fuppofed that all the 

 particles of the gas take the temperature which they acquire 

 by the contad of the covering of the balloon alone, and how 

 can it be conceived, that the lower particles, which are con» 

 tiguous to that portion of the covering which does not receive 

 the folar emanations, fliould be carried towards that which is ex- 

 pofed to it? And fince thefe particles at each conladl only 

 receive a part of the temperature to which they attain, what 

 a prodigious whirlwind muil there be fuppofed to be in the 

 gas! 



It appears to me, that the elaftic fluids, inftead of being The flow eon- 

 bad condudors, pofl"efs this property in a high degree, al- ^''^'"8 ''^ '°"* 

 though they probably differ from each other in this refpedt ; cribed to fomc 

 and if air which is confined produces effeds which fcem to modification, 

 prove the contrary, they are owing to fome circumftance 

 which modifies this property. 



I think it is probable, that this circumftance is the ftate ofThe gas Is pro- 



compreffion produced in a gas whirh cannot acquire a dilata- ^''''^ prevented 



-..,,, " . , r , irom acquiring 



tJion luitable to the temperature it receives ; we have leen that heat, becaufe ie 



caloric, in combining with the gafes, only raifes the tempera- cannot expand in 

 tare becaufe the dilatation meets with an obftacle (107); 

 hence it refults, that the further the air is removed from the 

 ftate of dilatation, which it fliould have, to be in equilibrium 

 of temperature, the greater refiftance will it oppoie to the 

 combination of the caloric, and the more will it lofe of its 

 conduding faculty, fo that the air which would take the 

 temperature of the furrounding bodies with facility, if it 

 could acquire fuitable dimenfions under a given prefliire, 

 becomes a worfe and worfe condudor in proportion as it re- 

 ceives a temperature farther removed from the dimenfions 

 which it can take. The air then experiences an efied, which 

 may be compared to that of a body in which the force of 

 cohefion obftruds the adion of a liquid, which can effed its 

 folution as foon as this obftrudion begins to be diminiftied. 



This explanation is applicable to the confervative property The effeft of 

 of heat, which Rumford has proved to belong to the air ^^t'is^Tto 

 which adheres to particles, fuch as thofe of the eider-down ; prevent the 



currents, than t« 



♦ Defcrip. de Tatroftat de I'Acad. de Dijon. oppofe the ex- 



this 



