56 Of the Management of Fire 



vantageous Forms for Boilers. General Principles 

 on which Boilers of all Dimensions ought to be con- 

 structed. 



IF flame be merely vapour, or a mixture of air and 

 steam heated red-hot, as air and steam are both non- 

 conductors of heat, there seems to be no difficulty in 

 conceiving that flame may, notwithstanding its great 

 degree of heat, still retain the properties of its compo- 

 nent fluids, and remain a non-conductor of heat. The 

 non-conducting power of air does not appear to be at all 

 impaired by being heated to the temperature of boiling 

 water; and I see no reason why that property in air, or 

 in any other elastic fluid, should be impaired by any 

 augmentation of temperature, however great. If steam, 

 or if air, at the temperature of 2 1 2 degrees of Fahren- 

 heit's thermometer, be a non-conductor of heat, why 

 should it not remain a non-conductor at that of 1000 

 degrees, or when heated red-hot ? I confess I do not 

 see how a body could be deprived of a property so essen- 

 tial, without being at the same time totally changed ; 

 and I believe nobody will imagine that either air or 

 steam undergoes any chemical change merely by being 

 heated to the temperature of red-hot iron. But without 

 insisting upon these reasonings, however conclusive I 

 may think them, I shall endeavour to show, from ex- 

 periment and observation, in short to prove, that flame 

 is in fact a non-conductor of heat. 



Taking it for granted what I imagine will not be 

 denied that air is a non-conductor of heat, at least 

 in the sense I have used that appellation, I shall 

 endeavour to show that flame acts precisely in the 

 same manner as a hot wind would do in communicat- 



