ON THE TRANSMISSION OF HEAT. 24*9 



with any other folid may at temperatures below its melting 

 point conduct caloric ; but as it cannot poflibly exift with a 

 temperature above 32°, it cannot communicate any tempe- 

 rature above that to a fluid in contact vvith it, and confequently 

 it ?ou!d not contribute in the above experiments to raife the 

 thermometer above that temperature. 



The experiment was performed in fuch a manner that no neither was the 

 motion was occafioned in the fluid capable of conveying any U! agl a 

 part of it directly heated to the bulb of* the thermometer ; and 

 indeed the regular, and in fome of the experiments, the flow , 



rife of the thermometer is inconfiftent with the fuppofition of 

 caloric being communicated by any caufeof this kind. 



It has been proved, that any current produced in the fluid nor c ° H!dan y 

 / 1,11 heated current 



by the contact of the heated folid could not be the mean of defcend j 



conveying caloric ; for if the fluid be fuppofed to have no con- 

 ducting power, fince the fides of the vefl'el are likewife inca- 

 pable of communicating any increafe of temperature, the por- 

 tion of fluid beneath the furface could not .poflibly be difturbed 

 by a heated folid merely reft ing on that furface. Even if the 

 folid were immerfed to fome depth in the fluid, it is only from 

 the fides and under part of it that a current could rife, and of 

 courfe no part beneath that level could be affected. 



It lias likewife been fliewn, that the rife of the thermome- nor did the mafs 

 ter cannot be afcribed to the contact of particles directly heated j^^e ro the 

 by the folid, and reaching the bulb from the finking of the thermometer j 

 column of fluid by the enlargement of the diameter of the vef- 

 fel from the melting of the ice ; ] ft. becaufe in the experiment 

 with the oil this finking did not take place, the water pro- 

 duced fupporting the oil at the fame height ; and 2dlv . be- 

 caufe even in the experiments with the mercury, the dimi- 

 mution did not take place to that extent which would have 

 been neceffary to have brought the particles which were heated 

 on the furface of the fluid into contact with the thermometer, 

 as was proved by actual meafurement, and by the phenomena 

 of the experiment itfelf. 



Lafily, the caloric which Teached the bulb of the thermo- nor was the heat 

 meter could not have been propagated by radiation, becaufe ^"nfnmted.by 

 caloric, it has been proved, does not radiate through tranfpa- 

 re.nt fluids ; and it cannot even be fuppofed capable of palling 

 by radiation through an opaque fluid as mercury. The lait 

 point is obvious, and is of itfelf decifive vvith rcfpect to this 



objection. 



