• N TME iL ATVRE 0¥ HEAT. 2QV 



feorizontal veflel employed 38|- minutes. By referring tbefe 

 fa6ls to computation, the Count finds that the heat loft by 

 adual communication to the air, is nearly ^y part of the whole 

 lofs. 



Exp. 32. The counter radiation by the platter, v;hich was Exp. 32. Veb- 

 ftated under the laft experiment as impeding the coolincr pr«- retarded "bVthe 

 cefs, affords the important profpecl of explaining the effetl of vicinity of other 

 clothing, and therefore deferved to be more fully examined. ' '^f' ^"^^ 

 The experiments 29 and 30 were therefore repeated, with tlie 

 diftance of three inches only between the bottom of each velTel 

 and its correfponding platter. The times of cooling through 

 iO^, were now 33| minutes and 40| minutes. 



Exp. 33. And when the diftance was diminifhed to two Exp. 33. Repe- 

 ijiches, the times proved 32y minutes and 42|: minutes. 

 . Thefe experiments fhew that the vicinity of a cold body, The vicinity of 

 of which the low temperature is not kept up by artificial 5^J"^„ fu"cefl 

 means, retards the cooling of a hot body. And from this fion will confti- 

 fea the Count concludes, that if the hot body had been a '"^^ — ^^^^^°S ' 

 •globe fufpended in the center of another larger thin hollow 

 i'phere, of the fame temperature, at the commencement, as 

 -the air and walls oF the roora^, the cooling would have been ' 

 more flow than if the external globe had not been prefent ; 

 and alfo, if the external globe itfelf were included in another 

 globe of the fame defcription, the retardation would have 

 been ftili more confiderable. And by extending this fuppofed 

 experiment to a number of thin concentric hollow fpheres, we 

 may conceive a great retardation to follow, and fliall become 

 acquainted with the nature of the eff'eds which take place 

 when a hot body is furrounded by proper clothing. 



. If the fpheres were metallic, the cooling would be flower more effeftuallf 

 if the furfaces were polilhed than if unpoliflied or blackened ;poHfhed^"^ ^ 

 "whence it is highly probable, that the warmth of any clothing 

 depends very much upon the polifli of its furface. 



The microfcope (hews that thofe fubftances which fuppIyFurs, feathers, 

 us with the warmeft coverings, fuch as furs, feathers, fJlks,J^^ ^* ^y^\ 

 and the like, have their furfaces highly poliflied; and the 

 finer the fibres, or the greater number of interpofed poliflied 

 furfaces, the warmer is the clothing. 



^ In the former experiments of Count Rumford, he confidered Clothing defends 

 I the warmth of clothing as prin^-ipally depending on the ob-^JJj^gfl^^J^g/jj 

 ilacles it oppofes to the motipn of the furrounding cold air ; preventing cir- 



V culation of the 

 air. 





