ON THE PASSAGE OF HEAT THROUGH FLUIDS. \ ($g 



In thefe experiments then a quantity of caloric was con- Whether the 

 veyed downwards through a portion of fluid, fo as to occafion ^ were thc fo]e 

 a confiderable rife of temperature in the thermometer, in the caufe of this 

 lft experiment to the extent of eight degrees in 15 minutes, tranfmiffion. 

 in the 2d, 8f degrees in 20 minutes. From thefe remits, the 

 conclufion might feem juft, that the fluid mult poffefs a cen- 

 ducling power. Further inveftigation, however, will fhew 

 that this is not fo certain, as at firft view it may appear. It is 

 rendered doubtful by the circumftance, that in all experiments 

 of this kind a quantity of caloric mull be conveyed by the 

 fides of the veflel. This quantity it is fcarcely poflible to af- 

 certain with any accuracy, and of courfe we are unable to de- 

 termine what fliare it has in occasioning the rife of tempera- 

 ture, and therefore whether it is the fole caufe, or whether 

 any part of that rife depends on the power the fluid has of 

 conducting caloric. 



That in thefe experiments caloric muft be conveyed to the Developementof 

 thermometer by means of the veflel in which the fluid is con- ^'™h ""fl ui'd is 

 fined, may be eafily fhewn. In the firft experiment, when heated down- 

 the heated oil was poured on the furfaceof the water, it came wards h"'™' 



r , taming veJJcU 



immediately in contact with the fides of the veflel. The glals 

 muft of courfe have been heated, and it would conduct caloric 

 in every direction. The portion of caloric conveyed down- 

 wards would again be communicated to the cold water in con- 

 tacl with the fides, this being expanded, and having its fpe- 

 cific gravity leflened could not remain touching the veflel, but 

 muft have formed a heated current rifing from its fides, and 

 extending beneath the oil. A defcending current muft con- 

 sequently have been formed in the axis of the veflel, and a 

 ftratum of heated water muft have been conftantly accumu- 

 lating. The thermometer would thus come to be affected 

 fooner or later, proportioned to the depth of the bulb in the 

 fluid, and it would continue to rife till the temperature of the 

 whole portion of fluid over it became nearly uniform. A 

 fimilar effect would be produced in the fecond experiment, as 

 the heated ball would immediately communicate part of its 

 caloric to the portion of water with which it came in contact, 

 and this flowing towards the fides of the veflel, and being 

 conftantly fucceeded by other heated portions, muft have 

 communicated caloric to the glafs. 



It 



