in Fluids. 345 



of air, has been rendered extremely probable I be- 

 lieve I might say proved by the experiments of which 

 I gave an account in one of my papers on Heat pub- 

 lished in the Transactions of the Royal Society ; and 

 I have shewn elsewhere (in my Sixth Essay) how much 

 reason there is to conclude that the particles of Steam 

 and of Flame are 'in the same predicament. 



But if all interchange and communication of Heat, 

 from particle to particle, immediately, or de proche en 

 proche, be absolutely impossible in so many elastic and 

 unelastic Fluids, and in Fluids so essentially different 

 in many other respects, are there not sufficient grounds 

 to conclude from hence, that this property is common to 

 all Fluids, and that it is even essential to fluidity? 



It is easy to conceive that the discovery of so impor- 

 tant a circumstance must necessarily occasion a consider- 

 able change in the ideas we have formed in respect to the 

 mechanical operations which take place in many of the 

 great phenomena of Nature ; as well as in many of 

 those still more interesting chemical operations, which 

 we are able to direct, but which we find, alas ! very dif- 

 ficult to explain. 



In my paper on Heat, above mentioned, published in 

 the Philosophical Transactions for the year 1792, j 

 endeavoured to apply the discovery of the non-conduct- 

 ing power of air in accounting for the warmth of the 

 hair of beasts, of the feathers of birds, of artificial 

 clothing, and of snow, the winter garment of the earth ; 

 and also, in explaining the causes of the cold winds 

 from the polar regions, and of their different directions 

 in different countries, which prevail at the end of winter, 

 and early in the spring. 



In my Sixth Essay (on the Management of Heat and 



