and the Economy of Fuel. 55 



if the air had been cooled (in mass), it seems highly 

 probable that the clouds would have returned. 



The results of these experiments compared with 

 those formerly alluded to, in which I had endeavoured 

 to ascertain the most advantageous forms for boilers, 

 opened to me an entirely new field for speculation and 

 for improvement in the management of fire. They 

 shewed me that not only cold air, but also hot air and 

 hot steam, and hot mixtures of air and steam, are non- 

 conductors of heat; consequently that the hot vapour 

 which rises from burning fuel, and even the flame itself ^ 

 is a non-conductor of heat. 



This may be thought a bold assertion ; but a little 

 calm reflection, and a careful examination of the phe- 

 nomena which attend the combustion of fuel, and the 

 communication of heat by flame, will show it to be well- 

 founded ; and the advantages which may be derived 

 from the knowledge of this fact are of very great im- 

 portance indeed. But this subject deserves to be thor- 

 oughly investigated. 



CHAPTER IV. 



Of the MANNER in which HEAT is COMMUNICATED by 

 FLAME to other Bodies. Flame acts on Bodies in 

 the same Manner as a hot Wind. The Effect of a 

 Blowpipe in increasing the Activity of Flame ex- 

 plained, and illustrated by Experiments. A Knowl- 

 edge of the Manner in which Heat is communicated 

 by Flame necessary in order to determine the most ad- 



