346 Of the Propagation of Heat 



the Economy of Fuel) I availed myself of the knowl- 

 edge of the non-conducting power of steam and of flame ', 

 in explaining the effects of a blow-pipe in increasing the 

 action of pure flame, and in investigating the most ad- 

 vantageous forms for boilers ; and in the Third Chapter 

 of this Essay I have endeavoured to apply the discov- 

 eries which have been made, respecting the manner in 

 which Heat is propagated in water, in explaining the 

 means which appear to have been used by the Creator 

 of the world for equalizing the temperatures of the dif- 

 ferent climates, and preventing the fatal effects of the 

 extremes of heat and of cold on the surface of the globe. 

 But a most interesting application remains to be made 

 of these discoveries, to chemistry, vegetation, and the 

 animal economy; and to the learned in those branches 

 of science I beg leave most earnestly to recommend 

 them. If I am not much mistaken, they will throw 

 a new light on many of those mysterious operations 

 of Nature, in which inanimate bodies are put in motion, 

 their forms changed, their component parts separated, 

 and new combinations formed ; and it is possible that 

 they may even enable us to account, on mechanical 

 principles, for those surprising appearances of prefer- 

 ence and predilection among bodies, which, without 

 ever having been attempted to be explained, have been 

 distinguished by the appellation of chemical affinity. 



Perhaps it will be found that every change of form, 

 in every kind of substance, is owing to Heat, and to 

 Heat alone ; that every concretion is a true congelation, 

 effected by cold or a diminution of Heat; and that 

 every change from a solid to a fluid form is a vt3\ fusion ; 

 that the difference between calcination in the wet and in 

 the dry way is, in fact, much less than has hitherto been 



