I^g ON' FLUIDS AS CONDUCTORS OF HEAT, 



2d. He froze the water at the furface of mercury cooled by 

 a frigorjfic mixture; the temperature of the mercury was there- 

 fore communicated to the water, and the latter yielded its ca- 

 loric to the mercury, to replace that which it loft. 



If the communication of heat was only the effect of the par- 

 ticles of a liquid, the mercury of a thermometer would fcarcely 

 change its temperature when it had arrived at the freezing point 

 of water: in fact in feveral of his experiments (Effayl ,) Rum- 

 ford fuppofes, that at this degree, the mercury no longer com- 

 municates heat : now a tliermometer takes the temperature of 

 neighbouring bodies very rapidly, and indicates it feveral de- 

 grees below the freezing point of water, and as far as its own 

 congelation; then it conduds itfelf like the folid bodies, and its 

 dilatations become proportionably fmaller than the preceding. 

 Mercury eon- Rumford has proved that the conducing power of mercury 



dcnfer, has iefs This effed of the mercury, wliich takes the temperature of 

 'T'^'i'""* *'^*^ fyftem in which it is placed more rapidly than the water, 

 although it has a much greater fpecific gravity, and is much Iefs 

 dilatable by the fame degrees of heat, and confequently the 

 heat will caufe much Iefs locomotion in its particles than in thofe 

 of water; this effe6l I fay, proves that the changes of tempe- 

 ature do not depend on the immediate communication and the 

 changes of fpecific gravity wliich produces the approximation 

 of the particles of unequal temperatures, but alio on the better 

 or worfe conducing property of each fubflance. 

 Rumford neg- 3d. Rumford paid no attention to the radiant caloric, nor 

 heat. " '^" did he make any allowance for it; neverthelefs the communi- 

 cation of heat efiabliftied by its means between folid bodies 

 and liquids, through the gafes, cannot be doubted, and it may 

 be remarked that when he brought a, heated bullet near to ice 

 and tallow, a communication of heat took place which melted 

 the furface of both, v^ iihout it being poffible to attribute this 

 communication to a circulation fuch as he thinks is neceffary. 

 Ixperlrtients of The ingenious experiments of Rumford have employed the 

 the s^ ' talents of feveral pHilofophers, who have already proved that 



the principles to which they led were not conformable to the 

 true refults of obfervation. 



Nicholfon found Nicholfon, in conjundion with Pi6iet, made fome experi- 

 heat to pafs , , • , , , . , i •■ i . 



downwards ments by which he proved, that, on heating a Mquid at th« 



tferough a fluid, furface, by the fuperpcfilion of a body, the heat penetrated^ 



and. 

 2 



